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 $58.98   3.351%   $60.9564   $60.96   $60.95   $61.00  
  Purchase #2 $237.78   10.564%   $262.8991   $262.90   $262.90   $262.90  
  Purchase #3 $171.56   9.310%   $187.5322   $187.53   $187.55   $187.50  
  Purchase #4 $42.54   9.612%   $46.6289   $46.63   $46.65   $46.60  
  Purchase #5 $16.99   11.495%   $18.943   $18.94   $18.95   $18.90  
  Purchase #6 $140.28   8.549%   $152.2725   $152.27   $152.25   $152.30  
  Purchase #7 $91.72   5.683%   $96.9324   $96.93   $96.95   $96.90  
  7 purchase totals = $759.85       $826.1645   $826.16   $826.20   $826.10