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 $48.26   8.874%   $52.5426   $52.54   $52.55   $52.50  
  Purchase #2 $194.62   10.199%   $214.4693   $214.47   $214.45   $214.50  
  Purchase #3 $204.85   10.778%   $226.9287   $226.93   $226.95   $226.90  
  Purchase #4 $65.28   3.274%   $67.4173   $67.42   $67.40   $67.40  
  Purchase #5 $220.92   9.554%   $242.0267   $242.03   $242.05   $242.00  
  Purchase #6 $201.98   13.113%   $228.4656   $228.47   $228.45   $228.50  
  Purchase #7 $210.99   5.111%   $221.7737   $221.77   $221.75   $221.80  
  7 purchase totals = $1,146.90       $1,253.6239   $1,253.63   $1,253.60   $1,253.60