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 $53.45   13.179%   $60.4942   $60.49   $60.50   $60.50  
  Purchase #2 $108.38   8.494%   $117.5858   $117.59   $117.60   $117.60  
  Purchase #3 $225.28   4.785%   $236.0596   $236.06   $236.05   $236.10  
  Purchase #4 $243.28   11.324%   $270.829   $270.83   $270.85   $270.80  
  Purchase #5 $97.71   5.548%   $103.131   $103.13   $103.15   $103.10  
  Purchase #6 $241.90   7.746%   $260.6376   $260.64   $260.65   $260.60  
  Purchase #7 $228.49   7.805%   $246.3236   $246.32   $246.30   $246.30  
  7 purchase totals = $1,198.49       $1,295.0608   $1,295.06   $1,295.10   $1,295.00