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 $194.29   7.334%   $208.5392   $208.54   $208.55   $208.50  
  Purchase #2 $223.95   5.866%   $237.0869   $237.09   $237.10   $237.10  
  Purchase #3 $6.76   12.493%   $7.6045   $7.60   $7.60   $7.60  
  Purchase #4 $88.70   6.407%   $94.383   $94.38   $94.40   $94.40  
  Purchase #5 $57.94   4.708%   $60.6678   $60.67   $60.65   $60.70  
  Purchase #6 $161.90   6.409%   $172.2762   $172.28   $172.30   $172.30  
  Purchase #7 $171.95   8.722%   $186.9475   $186.95   $186.95   $186.90  
  7 purchase totals = $905.49       $967.5051   $967.51   $967.55   $967.50