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 $199.86   4.539%   $208.9316   $208.93   $208.95   $208.90  
  Purchase #2 $199.58   4.821%   $209.2018   $209.20   $209.20   $209.20  
  Purchase #3 $101.99   13.102%   $115.3527   $115.35   $115.35   $115.40  
  Purchase #4 $76.86   6.285%   $81.6907   $81.69   $81.70   $81.70  
  Purchase #5 $176.70   3.272%   $182.4816   $182.48   $182.50   $182.50  
  Purchase #6 $14.34   7.764%   $15.4534   $15.45   $15.45   $15.50  
  Purchase #7 $192.31   11.132%   $213.7179   $213.72   $213.70   $213.70  
  7 purchase totals = $961.64       $1,026.8297   $1,026.82   $1,026.85   $1,026.90