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 $183.57   6.528%   $195.5534   $195.55   $195.55   $195.60  
  Purchase #2 $94.47   8.867%   $102.8467   $102.85   $102.85   $102.80  
  Purchase #3 $246.67   4.321%   $257.3286   $257.33   $257.35   $257.30  
  Purchase #4 $166.41   13.111%   $188.228   $188.23   $188.25   $188.20  
  Purchase #5 $72.83   13.456%   $82.63   $82.63   $82.65   $82.60  
  Purchase #6 $85.78   10.361%   $94.6677   $94.67   $94.65   $94.70  
  Purchase #7 $14.32   3.477%   $14.8179   $14.82   $14.80   $14.80  
  7 purchase totals = $864.05       $936.0723   $936.08   $936.10   $936.00