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 $42.92   7.839%   $46.2845   $46.28   $46.30   $46.30  
  Purchase #2 $101.60   5.242%   $106.9259   $106.93   $106.95   $106.90  
  Purchase #3 $105.78   11.733%   $118.1912   $118.19   $118.20   $118.20  
  Purchase #4 $147.58   12.396%   $165.874   $165.87   $165.85   $165.90  
  Purchase #5 $229.47   6.478%   $244.3351   $244.34   $244.35   $244.30  
  Purchase #6 $100.27   10.225%   $110.5226   $110.52   $110.50   $110.50  
  Purchase #7 $86.80   7.547%   $93.3508   $93.35   $93.35   $93.40  
  7 purchase totals = $814.42       $885.4841   $885.48   $885.50   $885.50