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 $68.56   5.374%   $72.2444   $72.24   $72.25   $72.20  
  Purchase #2 $162.35   9.866%   $178.3675   $178.37   $178.35   $178.40  
  Purchase #3 $16.39   4.535%   $17.1333   $17.13   $17.15   $17.10  
  Purchase #4 $152.91   6.355%   $162.6274   $162.63   $162.65   $162.60  
  Purchase #5 $199.37   6.509%   $212.347   $212.35   $212.35   $212.30  
  Purchase #6 $20.89   10.649%   $23.1146   $23.11   $23.10   $23.10  
  Purchase #7 $93.52   3.665%   $96.9475   $96.95   $96.95   $96.90  
  7 purchase totals = $713.99       $762.7817   $762.78   $762.80   $762.60