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 $168.85   8.292%   $182.851   $182.85   $182.85   $182.90  
  Purchase #2 $107.30   5.766%   $113.4869   $113.49   $113.50   $113.50  
  Purchase #3 $118.57   11.546%   $132.2601   $132.26   $132.25   $132.30  
  Purchase #4 $223.91   8.377%   $242.6669   $242.67   $242.65   $242.70  
  Purchase #5 $175.96   4.222%   $183.389   $183.39   $183.40   $183.40  
  Purchase #6 $107.83   4.264%   $112.4279   $112.43   $112.45   $112.40  
  Purchase #7 $119.91   9.336%   $131.1048   $131.10   $131.10   $131.10  
  7 purchase totals = $1,022.33       $1,098.1866   $1,098.19   $1,098.20   $1,098.30