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 $184.44   9.575%   $202.1001   $202.10   $202.10   $202.10  
  Purchase #2 $191.43   5.789%   $202.5119   $202.51   $202.50   $202.50  
  Purchase #3 $54.97   10.278%   $60.6198   $60.62   $60.60   $60.60  
  Purchase #4 $16.95   3.603%   $17.5607   $17.56   $17.55   $17.60  
  Purchase #5 $5.61   6.829%   $5.9931   $5.99   $6.00   $6.00  
  Purchase #6 $196.90   4.778%   $206.3079   $206.31   $206.30   $206.30  
  Purchase #7 $29.37   5.154%   $30.8837   $30.88   $30.90   $30.90  
  7 purchase totals = $679.67       $725.9772   $725.97   $725.95   $726.00