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 $208.89   5.751%   $220.9033   $220.90   $220.90   $220.90  
  Purchase #2 $72.40   8.743%   $78.7299   $78.73   $78.75   $78.70  
  Purchase #3 $218.96   5.255%   $230.4663   $230.47   $230.45   $230.50  
  Purchase #4 $63.67   5.739%   $67.324   $67.32   $67.30   $67.30  
  Purchase #5 $162.31   9.696%   $178.0476   $178.05   $178.05   $178.00  
  Purchase #6 $248.31   6.804%   $265.205   $265.21   $265.20   $265.20  
  Purchase #7 $51.86   6.252%   $55.1023   $55.10   $55.10   $55.10  
  7 purchase totals = $1,026.40       $1,095.7784   $1,095.78   $1,095.75   $1,095.70