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	$180.94	13.130%	$204.6974	$204.70	$204.70	$204.70
Purchase #2	$172.39	7.426%	$185.1917	$185.19	$185.20	$185.20
Purchase #3	$85.49	5.627%	$90.3005	$90.30	$90.30	$90.30
Purchase #4	$169.63	4.267%	$176.8681	$176.87	$176.85	$176.90
Purchase #5	$215.26	7.286%	$230.9438	$230.94	$230.95	$230.90
Purchase #6	$95.83	4.637%	$100.2736	$100.27	$100.25	$100.30
Purchase #7	$150.78	12.844%	$170.1462	$170.15	$170.15	$170.10
7 purchase totals =	$1,070.32		$1,158.4213	$1,158.42	$1,158.40	$1,158.40