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 $101.62   12.212%   $114.0298   $114.03   $114.05   $114.00  
  Purchase #2 $138.62   10.517%   $153.1987   $153.20   $153.20   $153.20  
  Purchase #3 $6.45   11.587%   $7.1974   $7.20   $7.20   $7.20  
  Purchase #4 $89.95   3.461%   $93.0632   $93.06   $93.05   $93.10  
  Purchase #5 $180.48   6.753%   $192.6678   $192.67   $192.65   $192.70  
  Purchase #6 $208.94   8.212%   $226.0982   $226.10   $226.10   $226.10  
  Purchase #7 $219.90   7.763%   $236.9708   $236.97   $236.95   $237.00  
  7 purchase totals = $945.96       $1,023.2259   $1,023.23   $1,023.20   $1,023.30