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	$188.69	13.563%	$214.282	$214.28	$214.30	$214.30
Purchase #2	$78.48	6.679%	$83.7217	$83.72	$83.70	$83.70
Purchase #3	$123.79	3.314%	$127.8924	$127.89	$127.90	$127.90
Purchase #4	$137.50	5.493%	$145.0529	$145.05	$145.05	$145.10
Purchase #5	$78.28	8.699%	$85.0896	$85.09	$85.10	$85.10
Purchase #6	$49.28	10.717%	$54.5613	$54.56	$54.55	$54.60
Purchase #7	$144.31	13.737%	$164.1339	$164.13	$164.15	$164.10
7 purchase totals =	$800.33		$874.7338	$874.72	$874.75	$874.80