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 $195.95   3.112%   $202.048   $202.05   $202.05   $202.00  
  Purchase #2 $166.26   8.520%   $180.4254   $180.43   $180.45   $180.40  
  Purchase #3 $167.36   3.322%   $172.9197   $172.92   $172.90   $172.90  
  Purchase #4 $28.98   3.151%   $29.8932   $29.89   $29.90   $29.90  
  Purchase #5 $114.65   9.355%   $125.3755   $125.38   $125.40   $125.40  
  Purchase #6 $172.72   3.263%   $178.3559   $178.36   $178.35   $178.40  
  Purchase #7 $26.47   4.691%   $27.7117   $27.71   $27.70   $27.70  
  7 purchase totals = $872.39       $916.7294   $916.74   $916.75   $916.70