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	$88.33	7.362%	$94.8329	$94.83	$94.85	$94.80
Purchase #2	$42.28	10.342%	$46.6526	$46.65	$46.65	$46.70
Purchase #3	$197.97	13.263%	$224.2268	$224.23	$224.25	$224.20
Purchase #4	$101.99	12.256%	$114.4899	$114.49	$114.50	$114.50
Purchase #5	$99.54	12.294%	$111.7774	$111.78	$111.80	$111.80
Purchase #6	$9.36	10.168%	$10.3117	$10.31	$10.30	$10.30
Purchase #7	$43.66	4.389%	$45.5762	$45.58	$45.60	$45.60
7 purchase totals =	$583.13		$647.8675	$647.87	$647.95	$647.90