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 $68.63   6.740%   $73.2557   $73.26   $73.25   $73.30  
  Purchase #2 $85.73   13.497%   $97.301   $97.30   $97.30   $97.30  
  Purchase #3 $219.96   3.617%   $227.916   $227.92   $227.90   $227.90  
  Purchase #4 $155.61   3.788%   $161.5045   $161.50   $161.50   $161.50  
  Purchase #5 $10.98   7.594%   $11.8138   $11.81   $11.80   $11.80  
  Purchase #6 $26.86   3.258%   $27.7351   $27.74   $27.75   $27.70  
  Purchase #7 $145.87   9.326%   $159.4738   $159.47   $159.45   $159.50  
  7 purchase totals = $713.64       $758.9999   $759.00   $758.95   $759.00