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 $61.54   9.373%   $67.3081   $67.31   $67.30   $67.30  
  Purchase #2 $244.40   13.531%   $277.4698   $277.47   $277.45   $277.50  
  Purchase #3 $164.80   3.281%   $170.2071   $170.21   $170.20   $170.20  
  Purchase #4 $96.31   6.447%   $102.5191   $102.52   $102.50   $102.50  
  Purchase #5 $238.42   9.625%   $261.3679   $261.37   $261.35   $261.40  
  Purchase #6 $178.35   5.874%   $188.8263   $188.83   $188.85   $188.80  
  Purchase #7 $122.93   8.803%   $133.7515   $133.75   $133.75   $133.80  
  7 purchase totals = $1,106.75       $1,201.4498   $1,201.46   $1,201.40   $1,201.50