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 $246.86   6.211%   $262.1925   $262.19   $262.20   $262.20  
  Purchase #2 $83.51   12.147%   $93.654   $93.65   $93.65   $93.70  
  Purchase #3 $114.69   9.560%   $125.6544   $125.65   $125.65   $125.70  
  Purchase #4 $215.99   8.383%   $234.0964   $234.10   $234.10   $234.10  
  Purchase #5 $209.41   4.466%   $218.7623   $218.76   $218.75   $218.80  
  Purchase #6 $43.36   6.687%   $46.2595   $46.26   $46.25   $46.30  
  Purchase #7 $120.32   8.754%   $130.8528   $130.85   $130.85   $130.90  
  7 purchase totals = $1,034.14       $1,111.4719   $1,111.46   $1,111.45   $1,111.70