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 $60.36   12.163%   $67.7016   $67.70   $67.70   $67.70  
  Purchase #2 $112.76   3.660%   $116.887   $116.89   $116.90   $116.90  
  Purchase #3 $82.59   4.740%   $86.5048   $86.50   $86.50   $86.50  
  Purchase #4 $237.34   12.389%   $266.7441   $266.74   $266.75   $266.70  
  Purchase #5 $174.26   7.612%   $187.5247   $187.52   $187.50   $187.50  
  Purchase #6 $136.50   12.316%   $153.3113   $153.31   $153.30   $153.30  
  Purchase #7 $96.44   10.631%   $106.6925   $106.69   $106.70   $106.70  
  7 purchase totals = $900.25       $985.3660   $985.35   $985.35   $985.30