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	$172.83	12.327%	$194.1348	$194.13	$194.15	$194.10
Purchase #2	$39.40	5.590%	$41.6025	$41.60	$41.60	$41.60
Purchase #3	$81.87	12.733%	$92.2945	$92.29	$92.30	$92.30
Purchase #4	$18.89	4.279%	$19.6983	$19.70	$19.70	$19.70
Purchase #5	$148.77	10.665%	$164.6363	$164.64	$164.65	$164.60
Purchase #6	$118.66	7.656%	$127.7446	$127.74	$127.75	$127.70
Purchase #7	$183.74	3.531%	$190.2279	$190.23	$190.25	$190.20
7 purchase totals =	$764.16		$830.3389	$830.33	$830.40	$830.20