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 $175.60   11.602%   $195.9731   $195.97   $195.95   $196.00  
  Purchase #2 $79.78   7.333%   $85.6303   $85.63   $85.65   $85.60  
  Purchase #3 $215.30   12.768%   $242.7895   $242.79   $242.80   $242.80  
  Purchase #4 $185.32   5.373%   $195.2772   $195.28   $195.30   $195.30  
  Purchase #5 $62.93   11.485%   $70.1575   $70.16   $70.15   $70.20  
  Purchase #6 $106.83   11.298%   $118.8997   $118.90   $118.90   $118.90  
  Purchase #7 $200.75   6.817%   $214.4351   $214.44   $214.45   $214.40  
  7 purchase totals = $1,026.51       $1,123.1624   $1,123.17   $1,123.20   $1,123.20