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 $239.74   5.760%   $253.549   $253.55   $253.55   $253.50  
  Purchase #2 $217.82   13.380%   $246.9643   $246.96   $246.95   $247.00  
  Purchase #3 $95.85   12.650%   $107.975   $107.98   $108.00   $108.00  
  Purchase #4 $220.85   6.500%   $235.2053   $235.21   $235.20   $235.20  
  Purchase #5 $76.67   8.145%   $82.9148   $82.91   $82.90   $82.90  
  Purchase #6 $200.92   5.461%   $211.8922   $211.89   $211.90   $211.90  
  Purchase #7 $10.64   10.747%   $11.7835   $11.78   $11.80   $11.80  
  7 purchase totals = $1,062.49       $1,150.2841   $1,150.28   $1,150.30   $1,150.30