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 $70.33   8.394%   $76.2335   $76.23   $76.25   $76.20  
  Purchase #2 $149.97   5.453%   $158.1479   $158.15   $158.15   $158.10  
  Purchase #3 $147.59   6.157%   $156.6771   $156.68   $156.70   $156.70  
  Purchase #4 $84.63   13.819%   $96.325   $96.33   $96.35   $96.30  
  Purchase #5 $118.88   9.684%   $130.3923   $130.39   $130.40   $130.40  
  Purchase #6 $248.36   3.586%   $257.2662   $257.27   $257.25   $257.30  
  Purchase #7 $176.73   4.680%   $185.001   $185.00   $185.00   $185.00  
  7 purchase totals = $996.49       $1,060.0430   $1,060.05   $1,060.10   $1,060.00