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	$222.75	13.798%	$253.485	$253.49	$253.50	$253.50
Purchase #2	$9.42	9.579%	$10.3223	$10.32	$10.30	$10.30
Purchase #3	$63.45	6.621%	$67.651	$67.65	$67.65	$67.70
Purchase #4	$102.66	11.728%	$114.7	$114.70	$114.70	$114.70
Purchase #5	$151.82	9.245%	$165.8558	$165.86	$165.85	$165.90
Purchase #6	$247.68	4.385%	$258.5408	$258.54	$258.55	$258.50
Purchase #7	$122.84	8.150%	$132.8515	$132.85	$132.85	$132.90
7 purchase totals =	$920.62		$1,003.4064	$1,003.41	$1,003.40	$1,003.50