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	$113.87	4.160%	$118.607	$118.61	$118.60	$118.60
Purchase #2	$30.52	10.239%	$33.6449	$33.64	$33.65	$33.60
Purchase #3	$26.54	4.323%	$27.6873	$27.69	$27.70	$27.70
Purchase #4	$172.63	7.340%	$185.301	$185.30	$185.30	$185.30
Purchase #5	$140.27	8.284%	$151.89	$151.89	$151.90	$151.90
Purchase #6	$96.58	3.701%	$100.1544	$100.15	$100.15	$100.20
Purchase #7	$32.49	9.130%	$35.4563	$35.46	$35.45	$35.50
7 purchase totals =	$612.90		$652.7409	$652.74	$652.75	$652.80