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	$159.82	4.668%	$167.2804	$167.28	$167.30	$167.30
Purchase #2	$173.74	13.707%	$197.5545	$197.55	$197.55	$197.60
Purchase #3	$153.74	6.861%	$164.2881	$164.29	$164.30	$164.30
Purchase #4	$128.43	8.334%	$139.1334	$139.13	$139.15	$139.10
Purchase #5	$227.33	5.695%	$240.2764	$240.28	$240.30	$240.30
Purchase #6	$70.88	10.504%	$78.3252	$78.33	$78.35	$78.30
Purchase #7	$147.88	6.596%	$157.6342	$157.63	$157.65	$157.60
7 purchase totals =	$1,061.82		$1,144.4922	$1,144.49	$1,144.60	$1,144.50