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 $67.76   11.589%   $75.6127   $75.61   $75.60   $75.60  
  Purchase #2 $195.87   10.417%   $216.2738   $216.27   $216.25   $216.30  
  Purchase #3 $23.28   11.152%   $25.8762   $25.88   $25.90   $25.90  
  Purchase #4 $107.45   5.334%   $113.1814   $113.18   $113.20   $113.20  
  Purchase #5 $158.97   3.737%   $164.9107   $164.91   $164.90   $164.90  
  Purchase #6 $234.76   4.346%   $244.9627   $244.96   $244.95   $245.00  
  Purchase #7 $222.41   13.589%   $252.6333   $252.63   $252.65   $252.60  
  7 purchase totals = $1,010.50       $1,093.4508   $1,093.44   $1,093.45   $1,093.50