Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $210.48   10.665%   $232.9277   $232.93   $232.95   $232.90  
  Purchase #2 $223.62   13.275%   $253.3056   $253.31   $253.30   $253.30  
  Purchase #3 $156.72   10.434%   $173.0722   $173.07   $173.05   $173.10  
  Purchase #4 $183.31   12.650%   $206.4987   $206.50   $206.50   $206.50  
  Purchase #5 $92.86   9.784%   $101.9454   $101.95   $101.95   $101.90  
  Purchase #6 $136.76   12.191%   $153.4324   $153.43   $153.45   $153.40  
  Purchase #7 $91.92   13.262%   $104.1104   $104.11   $104.10   $104.10  
  7 purchase totals = $1,095.67       $1,225.2924   $1,225.30   $1,225.30   $1,225.20