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	$168.54	11.714%	$188.2828	$188.28	$188.30	$188.30
Purchase #2	$126.61	13.343%	$143.5036	$143.50	$143.50	$143.50
Purchase #3	$243.64	5.539%	$257.1352	$257.14	$257.15	$257.10
Purchase #4	$230.25	12.317%	$258.6099	$258.61	$258.60	$258.60
Purchase #5	$181.32	9.824%	$199.1329	$199.13	$199.15	$199.10
Purchase #6	$143.54	10.647%	$158.8227	$158.82	$158.80	$158.80
Purchase #7	$145.61	6.534%	$155.1242	$155.12	$155.10	$155.10
7 purchase totals =	$1,239.51		$1,360.6113	$1,360.60	$1,360.60	$1,360.50