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	$236.69	8.808%	$257.5377	$257.54	$257.55	$257.50
Purchase #2	$216.94	7.407%	$233.0087	$233.01	$233.00	$233.00
Purchase #3	$111.71	13.824%	$127.1528	$127.15	$127.15	$127.20
Purchase #4	$179.26	11.804%	$200.4199	$200.42	$200.40	$200.40
Purchase #5	$101.34	10.363%	$111.8419	$111.84	$111.85	$111.80
Purchase #6	$142.82	10.123%	$157.2777	$157.28	$157.30	$157.30
Purchase #7	$9.90	11.225%	$11.0113	$11.01	$11.00	$11.00
7 purchase totals =	$998.66		$1,098.2500	$1,098.25	$1,098.25	$1,098.20