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 $48.53   7.754%   $52.293   $52.29   $52.30   $52.30  
  Purchase #2 $190.85   13.226%   $216.0918   $216.09   $216.10   $216.10  
  Purchase #3 $68.98   7.708%   $74.297   $74.30   $74.30   $74.30  
  Purchase #4 $160.54   4.865%   $168.3503   $168.35   $168.35   $168.40  
  Purchase #5 $105.69   10.213%   $116.4841   $116.48   $116.50   $116.50  
  Purchase #6 $69.88   8.808%   $76.035   $76.04   $76.05   $76.00  
  Purchase #7 $54.33   5.563%   $57.3524   $57.35   $57.35   $57.40  
  7 purchase totals = $698.80       $760.9036   $760.90   $760.95   $761.00