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	$81.42	7.463%	$87.4964	$87.50	$87.50	$87.50
Purchase #2	$41.87	3.613%	$43.3828	$43.38	$43.40	$43.40
Purchase #3	$247.56	9.870%	$271.9942	$271.99	$272.00	$272.00
Purchase #4	$161.63	7.545%	$173.825	$173.83	$173.85	$173.80
Purchase #5	$101.36	10.323%	$111.8234	$111.82	$111.80	$111.80
Purchase #6	$71.71	8.637%	$77.9036	$77.90	$77.90	$77.90
Purchase #7	$221.77	12.422%	$249.3183	$249.32	$249.30	$249.30
7 purchase totals =	$927.32		$1,015.7437	$1,015.74	$1,015.75	$1,015.70