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 $90.63   4.312%   $94.538   $94.54   $94.55   $94.50  
  Purchase #2 $174.84   10.316%   $192.8765   $192.88   $192.90   $192.90  
  Purchase #3 $118.99   7.530%   $127.9499   $127.95   $127.95   $127.90  
  Purchase #4 $122.29   10.231%   $134.8015   $134.80   $134.80   $134.80  
  Purchase #5 $213.55   12.173%   $239.5454   $239.55   $239.55   $239.50  
  Purchase #6 $101.93   13.362%   $115.5499   $115.55   $115.55   $115.50  
  Purchase #7 $112.64   4.114%   $117.274   $117.27   $117.25   $117.30  
  7 purchase totals = $934.87       $1,022.5352   $1,022.54   $1,022.55   $1,022.40