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 $206.94   3.653%   $214.4995   $214.50   $214.50   $214.50  
  Purchase #2 $238.96   5.632%   $252.4182   $252.42   $252.40   $252.40  
  Purchase #3 $179.98   9.475%   $197.0331   $197.03   $197.05   $197.00  
  Purchase #4 $115.77   8.805%   $125.9635   $125.96   $125.95   $126.00  
  Purchase #5 $191.82   8.451%   $208.0307   $208.03   $208.05   $208.00  
  Purchase #6 $179.86   3.745%   $186.5958   $186.60   $186.60   $186.60  
  Purchase #7 $231.86   9.252%   $253.3117   $253.31   $253.30   $253.30  
  7 purchase totals = $1,345.19       $1,437.8525   $1,437.85   $1,437.85   $1,437.80