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 $118.63   6.746%   $126.6328   $126.63   $126.65   $126.60  
  Purchase #2 $90.29   4.200%   $94.0822   $94.08   $94.10   $94.10  
  Purchase #3 $14.65   3.609%   $15.1787   $15.18   $15.20   $15.20  
  Purchase #4 $226.66   4.457%   $236.7622   $236.76   $236.75   $236.80  
  Purchase #5 $89.69   5.847%   $94.9342   $94.93   $94.95   $94.90  
  Purchase #6 $128.63   10.321%   $141.9059   $141.91   $141.90   $141.90  
  Purchase #7 $176.48   5.255%   $185.754   $185.75   $185.75   $185.80  
  7 purchase totals = $845.03       $895.2500   $895.24   $895.30   $895.30