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 $214.46   7.561%   $230.6753   $230.68   $230.70   $230.70  
  Purchase #2 $127.32   11.296%   $141.7021   $141.70   $141.70   $141.70  
  Purchase #3 $156.81   12.704%   $176.7311   $176.73   $176.75   $176.70  
  Purchase #4 $67.94   13.728%   $77.2668   $77.27   $77.25   $77.30  
  Purchase #5 $70.47   7.233%   $75.5671   $75.57   $75.55   $75.60  
  Purchase #6 $78.91   7.246%   $84.6278   $84.63   $84.65   $84.60  
  Purchase #7 $129.48   12.680%   $145.8981   $145.90   $145.90   $145.90  
  7 purchase totals = $845.39       $932.4683   $932.48   $932.50   $932.50