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	$129.58	3.433%	$134.0285	$134.03	$134.05	$134.00
Purchase #2	$88.32	5.128%	$92.849	$92.85	$92.85	$92.80
Purchase #3	$47.30	10.303%	$52.1733	$52.17	$52.15	$52.20
Purchase #4	$46.40	7.806%	$50.022	$50.02	$50.00	$50.00
Purchase #5	$106.90	4.342%	$111.5416	$111.54	$111.55	$111.50
Purchase #6	$28.58	11.112%	$31.7558	$31.76	$31.75	$31.80
Purchase #7	$37.42	11.613%	$41.7656	$41.77	$41.75	$41.80
7 purchase totals =	$484.50		$514.1358	$514.14	$514.10	$514.10