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	$172.48	3.548%	$178.5996	$178.60	$178.60	$178.60
Purchase #2	$224.68	3.733%	$233.0673	$233.07	$233.05	$233.10
Purchase #3	$40.42	4.675%	$42.3096	$42.31	$42.30	$42.30
Purchase #4	$213.27	9.822%	$234.2174	$234.22	$234.20	$234.20
Purchase #5	$84.63	6.172%	$89.8534	$89.85	$89.85	$89.90
Purchase #6	$134.52	9.797%	$147.6989	$147.70	$147.70	$147.70
Purchase #7	$204.50	9.119%	$223.1484	$223.15	$223.15	$223.10
7 purchase totals =	$1,074.50		$1,148.8946	$1,148.90	$1,148.85	$1,148.90