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	$118.60	4.261%	$123.6535	$123.65	$123.65	$123.70
Purchase #2	$150.66	4.810%	$157.9067	$157.91	$157.90	$157.90
Purchase #3	$220.61	13.405%	$250.1828	$250.18	$250.20	$250.20
Purchase #4	$248.80	5.648%	$262.8522	$262.85	$262.85	$262.90
Purchase #5	$139.80	3.545%	$144.7559	$144.76	$144.75	$144.80
Purchase #6	$20.52	8.520%	$22.2683	$22.27	$22.25	$22.30
Purchase #7	$49.26	8.174%	$53.2865	$53.29	$53.30	$53.30
7 purchase totals =	$948.25		$1,014.9059	$1,014.91	$1,014.90	$1,015.10