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	$165.75	9.385%	$181.3056	$181.31	$181.30	$181.30
Purchase #2	$198.84	9.156%	$217.0458	$217.05	$217.05	$217.00
Purchase #3	$104.77	3.293%	$108.2201	$108.22	$108.20	$108.20
Purchase #4	$153.38	12.587%	$172.6859	$172.69	$172.70	$172.70
Purchase #5	$212.27	12.510%	$238.825	$238.83	$238.85	$238.80
Purchase #6	$80.38	9.388%	$87.9261	$87.93	$87.95	$87.90
Purchase #7	$174.41	6.405%	$185.581	$185.58	$185.60	$185.60
7 purchase totals =	$1,089.80		$1,191.5895	$1,191.61	$1,191.65	$1,191.50