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 $184.27   5.806%   $194.9687   $194.97   $194.95   $195.00  
  Purchase #2 $98.67   12.464%   $110.9682   $110.97   $110.95   $111.00  
  Purchase #3 $185.35   13.102%   $209.6346   $209.63   $209.65   $209.60  
  Purchase #4 $52.57   5.421%   $55.4198   $55.42   $55.40   $55.40  
  Purchase #5 $190.80   11.759%   $213.2362   $213.24   $213.25   $213.20  
  Purchase #6 $125.75   12.349%   $141.2789   $141.28   $141.30   $141.30  
  Purchase #7 $32.55   9.381%   $35.6035   $35.60   $35.60   $35.60  
  7 purchase totals = $869.96       $961.1099   $961.11   $961.10   $961.10