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	$148.77	4.635%	$155.6655	$155.67	$155.65	$155.70
Purchase #2	$190.35	3.118%	$196.2851	$196.29	$196.30	$196.30
Purchase #3	$45.42	9.707%	$49.8289	$49.83	$49.85	$49.80
Purchase #4	$133.92	10.612%	$148.1316	$148.13	$148.15	$148.10
Purchase #5	$59.35	13.196%	$67.1818	$67.18	$67.20	$67.20
Purchase #6	$241.99	11.520%	$269.8672	$269.87	$269.85	$269.90
Purchase #7	$133.30	10.253%	$146.9672	$146.97	$146.95	$147.00
7 purchase totals =	$953.10		$1,033.9273	$1,033.94	$1,033.95	$1,034.00