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 $41.49   11.155%   $46.1182   $46.12   $46.10   $46.10  
  Purchase #2 $214.92   7.778%   $231.6365   $231.64   $231.65   $231.60  
  Purchase #3 $107.50   3.431%   $111.1883   $111.19   $111.20   $111.20  
  Purchase #4 $87.75   6.734%   $93.6591   $93.66   $93.65   $93.70  
  Purchase #5 $41.82   11.276%   $46.5356   $46.54   $46.55   $46.50  
  Purchase #6 $221.32   7.375%   $237.6424   $237.64   $237.65   $237.60  
  Purchase #7 $126.44   6.664%   $134.866   $134.87   $134.85   $134.90  
  7 purchase totals = $841.24       $901.6461   $901.66   $901.65   $901.60