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 $176.97   11.234%   $196.8508   $196.85   $196.85   $196.90  
  Purchase #2 $205.99   10.729%   $228.0907   $228.09   $228.10   $228.10  
  Purchase #3 $158.86   9.695%   $174.2615   $174.26   $174.25   $174.30  
  Purchase #4 $45.51   5.209%   $47.8806   $47.88   $47.90   $47.90  
  Purchase #5 $244.77   3.203%   $252.61   $252.61   $252.60   $252.60  
  Purchase #6 $174.63   3.131%   $180.0977   $180.10   $180.10   $180.10  
  Purchase #7 $170.75   3.194%   $176.2038   $176.20   $176.20   $176.20  
  7 purchase totals = $1,177.48       $1,255.9951   $1,255.99   $1,256.00   $1,256.10