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 $184.83   8.313%   $200.1949   $200.19   $200.20   $200.20  
  Purchase #2 $112.49   4.279%   $117.3034   $117.30   $117.30   $117.30  
  Purchase #3 $215.97   11.697%   $241.232   $241.23   $241.25   $241.20  
  Purchase #4 $48.48   9.434%   $53.0536   $53.05   $53.05   $53.10  
  Purchase #5 $154.34   8.193%   $166.9851   $166.99   $167.00   $167.00  
  Purchase #6 $200.76   8.249%   $217.3207   $217.32   $217.30   $217.30  
  Purchase #7 $232.56   11.368%   $258.9974   $259.00   $259.00   $259.00  
  7 purchase totals = $1,149.43       $1,255.0871   $1,255.08   $1,255.10   $1,255.10