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 $94.96   3.573%   $98.3529   $98.35   $98.35   $98.40  
  Purchase #2 $164.99   11.242%   $183.5382   $183.54   $183.55   $183.50  
  Purchase #3 $194.62   3.617%   $201.6594   $201.66   $201.65   $201.70  
  Purchase #4 $196.55   5.575%   $207.5077   $207.51   $207.50   $207.50  
  Purchase #5 $18.45   3.562%   $19.1072   $19.11   $19.10   $19.10  
  Purchase #6 $176.39   8.215%   $190.8804   $190.88   $190.90   $190.90  
  Purchase #7 $29.52   12.213%   $33.1253   $33.13   $33.15   $33.10  
  7 purchase totals = $875.48       $934.1711   $934.18   $934.20   $934.20