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 $62.36   4.448%   $65.1338   $65.13   $65.15   $65.10  
  Purchase #2 $209.50   3.104%   $216.0029   $216.00   $216.00   $216.00  
  Purchase #3 $51.67   4.485%   $53.9874   $53.99   $54.00   $54.00  
  Purchase #4 $177.57   7.721%   $191.2802   $191.28   $191.30   $191.30  
  Purchase #5 $177.71   10.672%   $196.6752   $196.68   $196.70   $196.70  
  Purchase #6 $237.99   5.189%   $250.3393   $250.34   $250.35   $250.30  
  Purchase #7 $192.67   7.196%   $206.5345   $206.53   $206.55   $206.50  
  7 purchase totals = $1,109.47       $1,179.9533   $1,179.95   $1,180.05   $1,179.90