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 $184.75   6.491%   $196.7421   $196.74   $196.75   $196.70  
  Purchase #2 $46.39   13.335%   $52.5761   $52.58   $52.60   $52.60  
  Purchase #3 $112.60   4.739%   $117.9361   $117.94   $117.95   $117.90  
  Purchase #4 $112.79   5.518%   $119.0138   $119.01   $119.00   $119.00  
  Purchase #5 $196.26   5.152%   $206.3713   $206.37   $206.35   $206.40  
  Purchase #6 $110.73   5.865%   $117.2243   $117.22   $117.20   $117.20  
  Purchase #7 $208.86   13.139%   $236.3021   $236.30   $236.30   $236.30  
  7 purchase totals = $972.38       $1,046.1658   $1,046.16   $1,046.15   $1,046.10