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 $104.48   7.322%   $112.13   $112.13   $112.15   $112.10  
  Purchase #2 $212.40   12.778%   $239.5405   $239.54   $239.55   $239.50  
  Purchase #3 $240.82   9.197%   $262.9682   $262.97   $262.95   $263.00  
  Purchase #4 $92.58   5.119%   $97.3192   $97.32   $97.30   $97.30  
  Purchase #5 $134.26   6.829%   $143.4286   $143.43   $143.45   $143.40  
  Purchase #6 $240.96   8.335%   $261.044   $261.04   $261.05   $261.00  
  Purchase #7 $133.29   3.518%   $137.9791   $137.98   $138.00   $138.00  
  7 purchase totals = $1,158.79       $1,254.4096   $1,254.41   $1,254.45   $1,254.30