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 $25.44   3.569%   $26.348   $26.35   $26.35   $26.30  
  Purchase #2 $99.36   4.851%   $104.18   $104.18   $104.20   $104.20  
  Purchase #3 $70.26   9.719%   $77.0886   $77.09   $77.10   $77.10  
  Purchase #4 $48.96   8.514%   $53.1285   $53.13   $53.15   $53.10  
  Purchase #5 $6.25   11.633%   $6.9771   $6.98   $7.00   $7.00  
  Purchase #6 $235.71   10.507%   $260.476   $260.48   $260.50   $260.50  
  Purchase #7 $208.34   5.237%   $219.2508   $219.25   $219.25   $219.30  
  7 purchase totals = $694.32       $747.4490   $747.46   $747.55   $747.50