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 $90.91   4.569%   $95.0637   $95.06   $95.05   $95.10  
  Purchase #2 $58.48   13.183%   $66.1894   $66.19   $66.20   $66.20  
  Purchase #3 $155.25   8.533%   $168.4975   $168.50   $168.50   $168.50  
  Purchase #4 $179.26   8.801%   $195.0367   $195.04   $195.05   $195.00  
  Purchase #5 $153.61   8.648%   $166.8942   $166.89   $166.90   $166.90  
  Purchase #6 $107.90   13.317%   $122.269   $122.27   $122.25   $122.30  
  Purchase #7 $135.36   6.813%   $144.5821   $144.58   $144.60   $144.60  
  7 purchase totals = $880.77       $958.5326   $958.53   $958.55   $958.60