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 $88.62   5.221%   $93.2469   $93.25   $93.25   $93.20  
  Purchase #2 $216.89   7.129%   $232.3521   $232.35   $232.35   $232.40  
  Purchase #3 $202.93   9.332%   $221.8674   $221.87   $221.85   $221.90  
  Purchase #4 $130.41   5.629%   $137.7508   $137.75   $137.75   $137.80  
  Purchase #5 $164.86   10.660%   $182.4341   $182.43   $182.45   $182.40  
  Purchase #6 $131.28   13.479%   $148.9752   $148.98   $149.00   $149.00  
  Purchase #7 $126.92   9.125%   $138.5015   $138.50   $138.50   $138.50  
  7 purchase totals = $1,061.91       $1,155.1280   $1,155.13   $1,155.15   $1,155.20