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 $62.73   3.799%   $65.1131   $65.11   $65.10   $65.10  
  Purchase #2 $168.62   5.370%   $177.6749   $177.67   $177.65   $177.70  
  Purchase #3 $186.95   6.438%   $198.9858   $198.99   $199.00   $199.00  
  Purchase #4 $239.93   6.486%   $255.4919   $255.49   $255.50   $255.50  
  Purchase #5 $217.39   6.625%   $231.7921   $231.79   $231.80   $231.80  
  Purchase #6 $174.88   7.425%   $187.8648   $187.86   $187.85   $187.90  
  Purchase #7 $107.41   11.228%   $119.47   $119.47   $119.45   $119.50  
  7 purchase totals = $1,157.91       $1,236.3926   $1,236.38   $1,236.35   $1,236.50