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	$125.81	8.160%	$136.0761	$136.08	$136.10	$136.10
Purchase #2	$231.76	12.103%	$259.8099	$259.81	$259.80	$259.80
Purchase #3	$144.83	9.278%	$158.2673	$158.27	$158.25	$158.30
Purchase #4	$26.53	10.374%	$29.2822	$29.28	$29.30	$29.30
Purchase #5	$92.57	8.434%	$100.3774	$100.38	$100.40	$100.40
Purchase #6	$230.37	8.764%	$250.5596	$250.56	$250.55	$250.60
Purchase #7	$127.56	5.165%	$134.1485	$134.15	$134.15	$134.10
7 purchase totals =	$979.43		$1,068.5210	$1,068.53	$1,068.55	$1,068.60