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 $211.31   10.274%   $233.02   $233.02   $233.00   $233.00  
  Purchase #2 $12.53   13.497%   $14.2212   $14.22   $14.20   $14.20  
  Purchase #3 $141.56   10.354%   $156.2171   $156.22   $156.20   $156.20  
  Purchase #4 $250.83   4.306%   $261.6307   $261.63   $261.65   $261.60  
  Purchase #5 $67.94   12.610%   $76.5072   $76.51   $76.50   $76.50  
  Purchase #6 $170.91   3.420%   $176.7551   $176.76   $176.75   $176.80  
  Purchase #7 $172.28   3.106%   $177.631   $177.63   $177.65   $177.60  
  7 purchase totals = $1,027.36       $1,095.9823   $1,095.99   $1,095.95   $1,095.90