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 $33.35   11.490%   $37.1819   $37.18   $37.20   $37.20  
  Purchase #2 $104.39   5.717%   $110.358   $110.36   $110.35   $110.40  
  Purchase #3 $68.74   11.638%   $76.74   $76.74   $76.75   $76.70  
  Purchase #4 $131.62   11.619%   $146.9129   $146.91   $146.90   $146.90  
  Purchase #5 $95.77   8.703%   $104.1049   $104.10   $104.10   $104.10  
  Purchase #6 $195.85   7.359%   $210.2626   $210.26   $210.25   $210.30  
  Purchase #7 $68.87   6.703%   $73.4864   $73.49   $73.50   $73.50  
  7 purchase totals = $698.59       $759.0467   $759.04   $759.05   $759.10