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 $108.98   9.190%   $118.9953   $119.00   $119.00   $119.00  
  Purchase #2 $102.57   7.578%   $110.3428   $110.34   $110.35   $110.30  
  Purchase #3 $92.61   9.662%   $101.558   $101.56   $101.55   $101.60  
  Purchase #4 $82.54   6.121%   $87.5923   $87.59   $87.60   $87.60  
  Purchase #5 $159.45   3.739%   $165.4118   $165.41   $165.40   $165.40  
  Purchase #6 $206.97   7.664%   $222.8322   $222.83   $222.85   $222.80  
  Purchase #7 $135.73   9.520%   $148.6515   $148.65   $148.65   $148.70  
  7 purchase totals = $888.85       $955.3839   $955.38   $955.40   $955.40