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 $214.75   5.793%   $227.1905   $227.19   $227.20   $227.20  
  Purchase #2 $86.88   7.112%   $93.0589   $93.06   $93.05   $93.10  
  Purchase #3 $96.29   11.126%   $107.0032   $107.00   $107.00   $107.00  
  Purchase #4 $99.48   10.375%   $109.8011   $109.80   $109.80   $109.80  
  Purchase #5 $24.86   4.554%   $25.9921   $25.99   $26.00   $26.00  
  Purchase #6 $95.72   12.823%   $107.9942   $107.99   $108.00   $108.00  
  Purchase #7 $76.55   3.488%   $79.2201   $79.22   $79.20   $79.20  
  7 purchase totals = $694.53       $750.2601   $750.25   $750.25   $750.30