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 $54.84   13.811%   $62.414   $62.41   $62.40   $62.40  
  Purchase #2 $68.33   7.235%   $73.2737   $73.27   $73.25   $73.30  
  Purchase #3 $91.57   8.280%   $99.152   $99.15   $99.15   $99.20  
  Purchase #4 $8.73   11.278%   $9.7146   $9.71   $9.70   $9.70  
  Purchase #5 $208.41   11.865%   $233.1378   $233.14   $233.15   $233.10  
  Purchase #6 $176.96   3.109%   $182.4617   $182.46   $182.45   $182.50  
  Purchase #7 $233.57   7.705%   $251.5666   $251.57   $251.55   $251.60  
  7 purchase totals = $842.41       $911.7204   $911.71   $911.65   $911.80