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 $119.31   4.781%   $125.0142   $125.01   $125.00   $125.00  
  Purchase #2 $229.37   5.541%   $242.0794   $242.08   $242.10   $242.10  
  Purchase #3 $233.29   13.530%   $264.8541   $264.85   $264.85   $264.90  
  Purchase #4 $83.52   10.136%   $91.9856   $91.99   $92.00   $92.00  
  Purchase #5 $97.46   11.548%   $108.7147   $108.71   $108.70   $108.70  
  Purchase #6 $127.70   6.832%   $136.4245   $136.42   $136.40   $136.40  
  Purchase #7 $244.69   13.821%   $278.5086   $278.51   $278.50   $278.50  
  7 purchase totals = $1,135.34       $1,247.5811   $1,247.57   $1,247.55   $1,247.60