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	$174.56	3.718%	$181.0501	$181.05	$181.05	$181.10
Purchase #2	$210.65	13.286%	$238.637	$238.64	$238.65	$238.60
Purchase #3	$139.37	6.472%	$148.39	$148.39	$148.40	$148.40
Purchase #4	$78.58	5.422%	$82.8406	$82.84	$82.85	$82.80
Purchase #5	$46.82	7.626%	$50.3905	$50.39	$50.40	$50.40
Purchase #6	$194.29	11.759%	$217.1366	$217.14	$217.15	$217.10
Purchase #7	$146.32	5.126%	$153.8204	$153.82	$153.80	$153.80
7 purchase totals =	$990.59		$1,072.2652	$1,072.27	$1,072.30	$1,072.20