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 $168.70   11.652%   $188.3569   $188.36   $188.35   $188.40  
  Purchase #2 $237.83   10.173%   $262.0244   $262.02   $262.00   $262.00  
  Purchase #3 $242.51   12.629%   $273.1366   $273.14   $273.15   $273.10  
  Purchase #4 $60.71   3.560%   $62.8713   $62.87   $62.85   $62.90  
  Purchase #5 $229.54   9.252%   $250.777   $250.78   $250.80   $250.80  
  Purchase #6 $178.76   11.700%   $199.6749   $199.67   $199.65   $199.70  
  Purchase #7 $232.40   6.546%   $247.6129   $247.61   $247.60   $247.60  
  7 purchase totals = $1,350.45       $1,484.4540   $1,484.45   $1,484.40   $1,484.50