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 $57.51   8.116%   $62.1775   $62.18   $62.20   $62.20  
  Purchase #2 $173.68   5.338%   $182.951   $182.95   $182.95   $183.00  
  Purchase #3 $151.45   7.701%   $163.1132   $163.11   $163.10   $163.10  
  Purchase #4 $32.75   6.645%   $34.9262   $34.93   $34.95   $34.90  
  Purchase #5 $36.42   6.557%   $38.8081   $38.81   $38.80   $38.80  
  Purchase #6 $168.84   7.809%   $182.0247   $182.02   $182.00   $182.00  
  Purchase #7 $57.50   9.287%   $62.84   $62.84   $62.85   $62.80  
  7 purchase totals = $678.15       $726.8407   $726.84   $726.85   $726.80