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 $67.73   12.279%   $76.0466   $76.05   $76.05   $76.00  
  Purchase #2 $217.73   5.288%   $229.2436   $229.24   $229.25   $229.20  
  Purchase #3 $248.69   5.408%   $262.1392   $262.14   $262.15   $262.10  
  Purchase #4 $67.86   9.229%   $74.1228   $74.12   $74.10   $74.10  
  Purchase #5 $176.25   3.433%   $182.3007   $182.30   $182.30   $182.30  
  Purchase #6 $157.72   11.162%   $175.3247   $175.32   $175.30   $175.30  
  Purchase #7 $39.87   12.808%   $44.9765   $44.98   $45.00   $45.00  
  7 purchase totals = $975.85       $1,044.1541   $1,044.15   $1,044.15   $1,044.00