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 $149.28   4.625%   $156.1842   $156.18   $156.20   $156.20  
  Purchase #2 $172.60   12.254%   $193.7504   $193.75   $193.75   $193.80  
  Purchase #3 $44.30   10.334%   $48.878   $48.88   $48.90   $48.90  
  Purchase #4 $62.42   6.454%   $66.4486   $66.45   $66.45   $66.40  
  Purchase #5 $215.45   10.390%   $237.8353   $237.84   $237.85   $237.80  
  Purchase #6 $101.73   13.847%   $115.8166   $115.82   $115.80   $115.80  
  Purchase #7 $227.50   10.280%   $250.887   $250.89   $250.90   $250.90  
  7 purchase totals = $973.28       $1,069.8001   $1,069.81   $1,069.85   $1,069.80