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 $194.98   3.606%   $202.011   $202.01   $202.00   $202.00  
  Purchase #2 $9.27   9.864%   $10.1844   $10.18   $10.20   $10.20  
  Purchase #3 $86.98   13.158%   $98.4248   $98.42   $98.40   $98.40  
  Purchase #4 $178.71   4.799%   $187.2863   $187.29   $187.30   $187.30  
  Purchase #5 $50.64   5.282%   $53.3148   $53.31   $53.30   $53.30  
  Purchase #6 $99.83   13.414%   $113.2212   $113.22   $113.20   $113.20  
  Purchase #7 $90.64   13.210%   $102.6135   $102.61   $102.60   $102.60  
  7 purchase totals = $711.05       $767.0560   $767.04   $767.00   $767.00