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 $41.95   10.472%   $46.343   $46.34   $46.35   $46.30  
  Purchase #2 $240.92   11.862%   $269.4979   $269.50   $269.50   $269.50  
  Purchase #3 $117.32   4.646%   $122.7707   $122.77   $122.75   $122.80  
  Purchase #4 $171.42   6.141%   $181.9469   $181.95   $181.95   $181.90  
  Purchase #5 $204.71   4.256%   $213.4225   $213.42   $213.40   $213.40  
  Purchase #6 $70.42   11.596%   $78.5859   $78.59   $78.60   $78.60  
  Purchase #7 $14.66   12.852%   $16.5441   $16.54   $16.55   $16.50  
  7 purchase totals = $861.40       $929.1110   $929.11   $929.10   $929.00