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 $95.49   11.156%   $106.1429   $106.14   $106.15   $106.10  
  Purchase #2 $88.95   9.784%   $97.6529   $97.65   $97.65   $97.70  
  Purchase #3 $105.67   11.452%   $117.7713   $117.77   $117.75   $117.80  
  Purchase #4 $179.91   10.759%   $199.2665   $199.27   $199.25   $199.30  
  Purchase #5 $44.62   6.321%   $47.4404   $47.44   $47.45   $47.40  
  Purchase #6 $151.98   4.294%   $158.506   $158.51   $158.50   $158.50  
  Purchase #7 $200.78   10.147%   $221.1531   $221.15   $221.15   $221.20  
  7 purchase totals = $867.40       $947.9331   $947.93   $947.90   $948.00