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 $86.71   9.510%   $94.9561   $94.96   $94.95   $95.00  
  Purchase #2 $196.61   8.859%   $214.0277   $214.03   $214.05   $214.00  
  Purchase #3 $205.34   7.504%   $220.7487   $220.75   $220.75   $220.70  
  Purchase #4 $117.79   9.563%   $129.0543   $129.05   $129.05   $129.10  
  Purchase #5 $89.37   6.192%   $94.9038   $94.90   $94.90   $94.90  
  Purchase #6 $158.79   9.605%   $174.0418   $174.04   $174.05   $174.00  
  Purchase #7 $63.96   7.574%   $68.8043   $68.80   $68.80   $68.80  
  7 purchase totals = $918.57       $996.5367   $996.53   $996.55   $996.50