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 $194.53   5.363%   $204.9626   $204.96   $204.95   $205.00  
  Purchase #2 $94.31   9.490%   $103.26   $103.26   $103.25   $103.30  
  Purchase #3 $173.59   5.252%   $182.7069   $182.71   $182.70   $182.70  
  Purchase #4 $226.52   10.430%   $250.146   $250.15   $250.15   $250.10  
  Purchase #5 $5.67   6.222%   $6.0228   $6.02   $6.00   $6.00  
  Purchase #6 $10.71   10.532%   $11.838   $11.84   $11.85   $11.80  
  Purchase #7 $195.80   7.152%   $209.8036   $209.80   $209.80   $209.80  
  7 purchase totals = $901.13       $968.7399   $968.74   $968.70   $968.70