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	$153.86	3.591%	$159.3851	$159.39	$159.40	$159.40
Purchase #2	$207.78	7.546%	$223.4591	$223.46	$223.45	$223.50
Purchase #3	$198.65	13.707%	$225.879	$225.88	$225.90	$225.90
Purchase #4	$44.28	4.176%	$46.1291	$46.13	$46.15	$46.10
Purchase #5	$129.42	13.530%	$146.9305	$146.93	$146.95	$146.90
Purchase #6	$179.37	3.269%	$185.2336	$185.23	$185.25	$185.20
Purchase #7	$121.47	8.356%	$131.62	$131.62	$131.60	$131.60
7 purchase totals =	$1,034.83		$1,118.6364	$1,118.64	$1,118.70	$1,118.60