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	$151.95	5.321%	$160.0353	$160.04	$160.05	$160.00
Purchase #2	$82.80	10.126%	$91.1843	$91.18	$91.20	$91.20
Purchase #3	$120.59	8.158%	$130.4277	$130.43	$130.45	$130.40
Purchase #4	$249.25	12.242%	$279.7632	$279.76	$279.75	$279.80
Purchase #5	$156.52	10.322%	$172.676	$172.68	$172.70	$172.70
Purchase #6	$92.95	4.541%	$97.1709	$97.17	$97.15	$97.20
Purchase #7	$149.46	3.457%	$154.6268	$154.63	$154.65	$154.60
7 purchase totals =	$1,003.52		$1,085.8842	$1,085.89	$1,085.95	$1,085.90