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 $113.96   10.504%   $125.9304   $125.93   $125.95   $125.90  
  Purchase #2 $152.69   6.443%   $162.5278   $162.53   $162.55   $162.50  
  Purchase #3 $185.46   11.316%   $206.4467   $206.45   $206.45   $206.40  
  Purchase #4 $114.53   9.266%   $125.1423   $125.14   $125.15   $125.10  
  Purchase #5 $8.60   13.696%   $9.7779   $9.78   $9.80   $9.80  
  Purchase #6 $129.65   4.134%   $135.0097   $135.01   $135.00   $135.00  
  Purchase #7 $143.47   11.735%   $160.3062   $160.31   $160.30   $160.30  
  7 purchase totals = $848.36       $925.1410   $925.15   $925.20   $925.00