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 $186.99   5.462%   $197.2034   $197.20   $197.20   $197.20  
  Purchase #2 $226.94   5.446%   $239.2992   $239.30   $239.30   $239.30  
  Purchase #3 $17.63   10.465%   $19.475   $19.48   $19.50   $19.50  
  Purchase #4 $131.27   13.679%   $149.2264   $149.23   $149.25   $149.20  
  Purchase #5 $127.72   8.232%   $138.2339   $138.23   $138.25   $138.20  
  Purchase #6 $175.93   9.141%   $192.0118   $192.01   $192.00   $192.00  
  Purchase #7 $25.31   6.538%   $26.9648   $26.96   $26.95   $27.00  
  7 purchase totals = $891.79       $962.4145   $962.41   $962.45   $962.40