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 $116.26   8.494%   $126.1351   $126.14   $126.15   $126.10  
  Purchase #2 $56.51   10.588%   $62.4933   $62.49   $62.50   $62.50  
  Purchase #3 $119.85   3.834%   $124.445   $124.45   $124.45   $124.40  
  Purchase #4 $31.81   9.335%   $34.7795   $34.78   $34.80   $34.80  
  Purchase #5 $149.77   12.397%   $168.337   $168.34   $168.35   $168.30  
  Purchase #6 $190.50   3.787%   $197.7142   $197.71   $197.70   $197.70  
  Purchase #7 $32.35   5.775%   $34.2182   $34.22   $34.20   $34.20  
  7 purchase totals = $697.05       $748.1223   $748.13   $748.15   $748.00