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 $95.71   12.791%   $107.9523   $107.95   $107.95   $108.00  
  Purchase #2 $231.33   9.806%   $254.0142   $254.01   $254.00   $254.00  
  Purchase #3 $148.68   7.281%   $159.5054   $159.51   $159.50   $159.50  
  Purchase #4 $35.47   9.800%   $38.9461   $38.95   $38.95   $38.90  
  Purchase #5 $42.67   9.223%   $46.6055   $46.61   $46.60   $46.60  
  Purchase #6 $100.28   6.590%   $106.8885   $106.89   $106.90   $106.90  
  Purchase #7 $211.40   10.786%   $234.2016   $234.20   $234.20   $234.20  
  7 purchase totals = $865.54       $948.1136   $948.12   $948.10   $948.10