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 $62.48   10.727%   $69.1822   $69.18   $69.20   $69.20  
  Purchase #2 $184.64   5.766%   $195.2863   $195.29   $195.30   $195.30  
  Purchase #3 $84.98   13.573%   $96.5143   $96.51   $96.50   $96.50  
  Purchase #4 $50.64   12.491%   $56.9654   $56.97   $56.95   $57.00  
  Purchase #5 $212.56   7.367%   $228.2193   $228.22   $228.20   $228.20  
  Purchase #6 $6.81   5.286%   $7.17   $7.17   $7.15   $7.20  
  Purchase #7 $60.57   5.473%   $63.885   $63.89   $63.90   $63.90  
  7 purchase totals = $662.68       $717.2225   $717.23   $717.20   $717.30