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 $213.78   10.675%   $236.601   $236.60   $236.60   $236.60  
  Purchase #2 $60.92   8.313%   $65.9843   $65.98   $66.00   $66.00  
  Purchase #3 $104.25   7.188%   $111.7435   $111.74   $111.75   $111.70  
  Purchase #4 $154.28   12.216%   $173.1268   $173.13   $173.15   $173.10  
  Purchase #5 $53.43   7.635%   $57.5094   $57.51   $57.50   $57.50  
  Purchase #6 $191.79   4.316%   $200.0677   $200.07   $200.05   $200.10  
  Purchase #7 $238.53   11.280%   $265.4362   $265.44   $265.45   $265.40  
  7 purchase totals = $1,016.98       $1,110.4689   $1,110.47   $1,110.50   $1,110.40