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 $150.43   8.475%   $163.1789   $163.18   $163.20   $163.20  
  Purchase #2 $71.58   5.130%   $75.2521   $75.25   $75.25   $75.30  
  Purchase #3 $55.93   8.594%   $60.7366   $60.74   $60.75   $60.70  
  Purchase #4 $53.66   12.238%   $60.2269   $60.23   $60.25   $60.20  
  Purchase #5 $209.95   7.337%   $225.354   $225.35   $225.35   $225.40  
  Purchase #6 $103.55   11.188%   $115.1352   $115.14   $115.15   $115.10  
  Purchase #7 $23.98   5.460%   $25.2893   $25.29   $25.30   $25.30  
  7 purchase totals = $669.08       $725.1730   $725.18   $725.25   $725.20