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 $62.80   9.404%   $68.7057   $68.71   $68.70   $68.70  
  Purchase #2 $228.57   10.691%   $253.0064   $253.01   $253.00   $253.00  
  Purchase #3 $105.73   12.240%   $118.6714   $118.67   $118.65   $118.70  
  Purchase #4 $8.63   12.473%   $9.7064   $9.71   $9.70   $9.70  
  Purchase #5 $51.49   8.278%   $55.7523   $55.75   $55.75   $55.80  
  Purchase #6 $139.61   8.163%   $151.0064   $151.01   $151.00   $151.00  
  Purchase #7 $205.96   6.529%   $219.4071   $219.41   $219.40   $219.40  
  7 purchase totals = $802.79       $876.2557   $876.27   $876.20   $876.30