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	$132.83	13.565%	$150.8484	$150.85	$150.85	$150.80
Purchase #2	$82.97	7.194%	$88.9389	$88.94	$88.95	$88.90
Purchase #3	$127.36	4.500%	$133.0912	$133.09	$133.10	$133.10
Purchase #4	$130.58	13.827%	$148.6353	$148.64	$148.65	$148.60
Purchase #5	$240.52	7.363%	$258.2295	$258.23	$258.25	$258.20
Purchase #6	$69.40	13.744%	$78.9383	$78.94	$78.95	$78.90
Purchase #7	$138.78	13.375%	$157.3418	$157.34	$157.35	$157.30
7 purchase totals =	$922.44		$1,016.0234	$1,016.03	$1,016.10	$1,015.80