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 $116.63   8.670%   $126.7418   $126.74   $126.75   $126.70  
  Purchase #2 $33.34   8.319%   $36.1136   $36.11   $36.10   $36.10  
  Purchase #3 $92.53   7.526%   $99.4938   $99.49   $99.50   $99.50  
  Purchase #4 $107.59   7.724%   $115.9003   $115.90   $115.90   $115.90  
  Purchase #5 $210.94   9.513%   $231.0067   $231.01   $231.00   $231.00  
  Purchase #6 $100.35   11.209%   $111.5982   $111.60   $111.60   $111.60  
  Purchase #7 $214.87   7.550%   $231.0927   $231.09   $231.10   $231.10  
  7 purchase totals = $876.25       $951.9471   $951.94   $951.95   $951.90