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	$68.26	5.570%	$72.0621	$72.06	$72.05	$72.10
Purchase #2	$93.31	9.235%	$101.9272	$101.93	$101.95	$101.90
Purchase #3	$103.84	13.105%	$117.4482	$117.45	$117.45	$117.40
Purchase #4	$32.44	7.418%	$34.8464	$34.85	$34.85	$34.80
Purchase #5	$151.89	3.199%	$156.749	$156.75	$156.75	$156.70
Purchase #6	$155.85	11.601%	$173.9302	$173.93	$173.95	$173.90
Purchase #7	$85.42	6.301%	$90.8023	$90.80	$90.80	$90.80
7 purchase totals =	$691.01		$747.7654	$747.77	$747.80	$747.60