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 $193.53   3.671%   $200.6345   $200.63   $200.65   $200.60  
  Purchase #2 $238.63   10.194%   $262.9559   $262.96   $262.95   $263.00  
  Purchase #3 $207.72   8.818%   $226.0367   $226.04   $226.05   $226.00  
  Purchase #4 $149.44   5.230%   $157.2557   $157.26   $157.25   $157.30  
  Purchase #5 $67.70   7.533%   $72.7998   $72.80   $72.80   $72.80  
  Purchase #6 $91.37   11.197%   $101.6007   $101.60   $101.60   $101.60  
  Purchase #7 $205.69   4.278%   $214.4894   $214.49   $214.50   $214.50  
  7 purchase totals = $1,154.08       $1,235.7727   $1,235.78   $1,235.80   $1,235.80