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 $59.46   4.604%   $62.1975   $62.20   $62.20   $62.20  
  Purchase #2 $78.63   5.872%   $83.2472   $83.25   $83.25   $83.20  
  Purchase #3 $235.73   5.219%   $248.0327   $248.03   $248.05   $248.00  
  Purchase #4 $60.64   4.392%   $63.3033   $63.30   $63.30   $63.30  
  Purchase #5 $21.84   8.252%   $23.6422   $23.64   $23.65   $23.60  
  Purchase #6 $61.26   3.355%   $63.3153   $63.32   $63.30   $63.30  
  Purchase #7 $203.68   5.164%   $214.198   $214.20   $214.20   $214.20  
  7 purchase totals = $721.24       $757.9362   $757.94   $757.95   $757.80