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 $64.86   10.737%   $71.824   $71.82   $71.80   $71.80  
  Purchase #2 $222.94   13.174%   $252.3101   $252.31   $252.30   $252.30  
  Purchase #3 $109.81   9.108%   $119.8115   $119.81   $119.80   $119.80  
  Purchase #4 $201.86   9.123%   $220.2757   $220.28   $220.30   $220.30  
  Purchase #5 $83.72   3.515%   $86.6628   $86.66   $86.65   $86.70  
  Purchase #6 $215.41   12.746%   $242.8662   $242.87   $242.85   $242.90  
  Purchase #7 $94.63   8.343%   $102.525   $102.53   $102.55   $102.50  
  7 purchase totals = $993.23       $1,096.2753   $1,096.28   $1,096.25   $1,096.30