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	$151.45	4.626%	$158.4561	$158.46	$158.45	$158.50
Purchase #2	$179.85	3.660%	$186.4325	$186.43	$186.45	$186.40
Purchase #3	$231.94	4.768%	$242.9989	$243.00	$243.00	$243.00
Purchase #4	$156.80	10.742%	$173.6435	$173.64	$173.65	$173.60
Purchase #5	$209.42	11.457%	$233.4132	$233.41	$233.40	$233.40
Purchase #6	$139.61	9.448%	$152.8004	$152.80	$152.80	$152.80
Purchase #7	$112.95	12.463%	$127.027	$127.03	$127.05	$127.00
7 purchase totals =	$1,182.02		$1,274.7716	$1,274.77	$1,274.80	$1,274.70