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	$181.92	5.824%	$192.515	$192.52	$192.50	$192.50
Purchase #2	$173.55	5.151%	$182.4896	$182.49	$182.50	$182.50
Purchase #3	$48.30	12.604%	$54.3877	$54.39	$54.40	$54.40
Purchase #4	$155.53	7.487%	$167.1745	$167.17	$167.15	$167.20
Purchase #5	$126.28	13.859%	$143.7811	$143.78	$143.80	$143.80
Purchase #6	$31.70	3.501%	$32.8098	$32.81	$32.80	$32.80
Purchase #7	$107.87	3.368%	$111.5031	$111.50	$111.50	$111.50
7 purchase totals =	$825.15		$884.6608	$884.66	$884.65	$884.70