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	$129.76	13.765%	$147.6215	$147.62	$147.60	$147.60
Purchase #2	$174.71	7.812%	$188.3583	$188.36	$188.35	$188.40
Purchase #3	$151.42	13.792%	$172.3038	$172.30	$172.30	$172.30
Purchase #4	$250.25	9.528%	$274.0938	$274.09	$274.10	$274.10
Purchase #5	$241.68	5.585%	$255.1778	$255.18	$255.20	$255.20
Purchase #6	$99.54	12.344%	$111.8272	$111.83	$111.85	$111.80
Purchase #7	$137.87	10.356%	$152.1478	$152.15	$152.15	$152.10
7 purchase totals =	$1,185.23		$1,301.5302	$1,301.53	$1,301.55	$1,301.50