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 $86.53   8.365%   $93.7682   $93.77   $93.75   $93.80  
  Purchase #2 $119.90   6.551%   $127.7546   $127.75   $127.75   $127.80  
  Purchase #3 $145.78   9.353%   $159.4148   $159.41   $159.40   $159.40  
  Purchase #4 $23.44   5.272%   $24.6758   $24.68   $24.70   $24.70  
  Purchase #5 $126.55   13.310%   $143.3938   $143.39   $143.40   $143.40  
  Purchase #6 $128.69   13.517%   $146.085   $146.09   $146.10   $146.10  
  Purchase #7 $241.96   4.738%   $253.4241   $253.42   $253.40   $253.40  
  7 purchase totals = $872.85       $948.5163   $948.51   $948.50   $948.60