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 $84.60   12.847%   $95.4686   $95.47   $95.45   $95.50  
  Purchase #2 $54.91   11.573%   $61.2647   $61.26   $61.25   $61.30  
  Purchase #3 $166.62   6.234%   $177.0071   $177.01   $177.00   $177.00  
  Purchase #4 $13.31   4.532%   $13.9132   $13.91   $13.90   $13.90  
  Purchase #5 $80.99   11.349%   $90.1816   $90.18   $90.20   $90.20  
  Purchase #6 $250.97   3.403%   $259.5105   $259.51   $259.50   $259.50  
  Purchase #7 $223.67   8.599%   $242.9034   $242.90   $242.90   $242.90  
  7 purchase totals = $875.07       $940.2491   $940.24   $940.20   $940.30