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 $214.87   9.255%   $234.7562   $234.76   $234.75   $234.80  
  Purchase #2 $58.59   5.873%   $62.031   $62.03   $62.05   $62.00  
  Purchase #3 $123.54   7.677%   $133.0242   $133.02   $133.00   $133.00  
  Purchase #4 $231.60   8.340%   $250.9154   $250.92   $250.90   $250.90  
  Purchase #5 $162.64   13.720%   $184.9542   $184.95   $184.95   $185.00  
  Purchase #6 $105.96   8.865%   $115.3534   $115.35   $115.35   $115.40  
  Purchase #7 $208.57   3.500%   $215.87   $215.87   $215.85   $215.90  
  7 purchase totals = $1,105.77       $1,196.9044   $1,196.90   $1,196.85   $1,197.00