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	$172.53	13.790%	$196.3219	$196.32	$196.30	$196.30
Purchase #2	$214.66	13.537%	$243.7185	$243.72	$243.70	$243.70
Purchase #3	$51.32	9.476%	$56.1831	$56.18	$56.20	$56.20
Purchase #4	$67.42	5.869%	$71.3769	$71.38	$71.40	$71.40
Purchase #5	$82.96	11.695%	$92.6622	$92.66	$92.65	$92.70
Purchase #6	$120.89	5.701%	$127.7819	$127.78	$127.80	$127.80
Purchase #7	$76.60	9.248%	$83.684	$83.68	$83.70	$83.70
7 purchase totals =	$786.38		$871.7285	$871.72	$871.75	$871.80