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 $215.62   5.257%   $226.9551   $226.96   $226.95   $227.00  
  Purchase #2 $144.29   5.450%   $152.1538   $152.15   $152.15   $152.20  
  Purchase #3 $24.50   10.143%   $26.985   $26.99   $27.00   $27.00  
  Purchase #4 $233.32   4.693%   $244.2697   $244.27   $244.25   $244.30  
  Purchase #5 $166.42   12.431%   $187.1077   $187.11   $187.10   $187.10  
  Purchase #6 $27.44   3.156%   $28.306   $28.31   $28.30   $28.30  
  Purchase #7 $97.75   5.548%   $103.1732   $103.17   $103.15   $103.20  
  7 purchase totals = $909.34       $968.9505   $968.96   $968.90   $969.10