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	$70.44	4.451%	$73.5753	$73.58	$73.60	$73.60
Purchase #2	$58.25	5.355%	$61.3693	$61.37	$61.35	$61.40
Purchase #3	$211.85	5.657%	$223.8344	$223.83	$223.85	$223.80
Purchase #4	$18.42	13.106%	$20.8341	$20.83	$20.85	$20.80
Purchase #5	$157.43	10.812%	$174.4513	$174.45	$174.45	$174.50
Purchase #6	$57.65	10.758%	$63.852	$63.85	$63.85	$63.90
Purchase #7	$74.25	10.202%	$81.825	$81.83	$81.85	$81.80
7 purchase totals =	$648.29		$699.7414	$699.74	$699.80	$699.80