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	$14.42	10.601%	$15.9487	$15.95	$15.95	$15.90
Purchase #2	$87.92	12.772%	$99.1491	$99.15	$99.15	$99.10
Purchase #3	$17.30	5.230%	$18.2048	$18.20	$18.20	$18.20
Purchase #4	$92.61	4.645%	$96.9117	$96.91	$96.90	$96.90
Purchase #5	$101.25	8.397%	$109.752	$109.75	$109.75	$109.80
Purchase #6	$11.45	12.130%	$12.8389	$12.84	$12.85	$12.80
Purchase #7	$120.75	5.236%	$127.0725	$127.07	$127.05	$127.10
7 purchase totals =	$445.70		$479.8777	$479.87	$479.85	$479.80