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 $94.75   8.243%   $102.5602   $102.56   $102.55   $102.60  
  Purchase #2 $243.73   5.668%   $257.5446   $257.54   $257.55   $257.50  
  Purchase #3 $207.99   3.762%   $215.8146   $215.81   $215.80   $215.80  
  Purchase #4 $103.78   6.224%   $110.2393   $110.24   $110.25   $110.20  
  Purchase #5 $26.49   4.283%   $27.6246   $27.62   $27.60   $27.60  
  Purchase #6 $201.92   9.726%   $221.5587   $221.56   $221.55   $221.60  
  Purchase #7 $216.87   7.861%   $233.9182   $233.92   $233.90   $233.90  
  7 purchase totals = $1,095.53       $1,169.2602   $1,169.25   $1,169.20   $1,169.20