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 $92.71   4.145%   $96.5528   $96.55   $96.55   $96.60  
  Purchase #2 $92.28   6.786%   $98.5421   $98.54   $98.55   $98.50  
  Purchase #3 $98.52   13.872%   $112.1867   $112.19   $112.20   $112.20  
  Purchase #4 $146.74   4.491%   $153.3301   $153.33   $153.35   $153.30  
  Purchase #5 $247.41   8.687%   $268.9025   $268.90   $268.90   $268.90  
  Purchase #6 $28.55   8.773%   $31.0547   $31.05   $31.05   $31.10  
  Purchase #7 $129.95   3.410%   $134.3813   $134.38   $134.40   $134.40  
  7 purchase totals = $836.16       $894.9502   $894.94   $895.00   $895.00