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 $172.64   13.259%   $195.5303   $195.53   $195.55   $195.50  
  Purchase #2 $232.80   9.786%   $255.5818   $255.58   $255.60   $255.60  
  Purchase #3 $120.62   9.403%   $131.9619   $131.96   $131.95   $132.00  
  Purchase #4 $42.51   11.336%   $47.3289   $47.33   $47.35   $47.30  
  Purchase #5 $11.31   9.673%   $12.404   $12.40   $12.40   $12.40  
  Purchase #6 $97.96   5.837%   $103.6779   $103.68   $103.70   $103.70  
  Purchase #7 $205.77   5.576%   $217.2437   $217.24   $217.25   $217.20  
  7 purchase totals = $883.61       $963.7285   $963.72   $963.80   $963.70