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 $67.73   8.692%   $73.6171   $73.62   $73.60   $73.60  
  Purchase #2 $207.81   5.184%   $218.5829   $218.58   $218.60   $218.60  
  Purchase #3 $27.44   7.828%   $29.588   $29.59   $29.60   $29.60  
  Purchase #4 $42.96   10.376%   $47.4175   $47.42   $47.40   $47.40  
  Purchase #5 $56.86   4.395%   $59.359   $59.36   $59.35   $59.40  
  Purchase #6 $160.63   9.527%   $175.9332   $175.93   $175.95   $175.90  
  Purchase #7 $144.34   9.658%   $158.2804   $158.28   $158.30   $158.30  
  7 purchase totals = $707.77       $762.7781   $762.78   $762.80   $762.80