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	$94.45	10.860%	$104.7073	$104.71	$104.70	$104.70
Purchase #2	$134.44	10.142%	$148.0749	$148.07	$148.05	$148.10
Purchase #3	$61.77	13.775%	$70.2788	$70.28	$70.30	$70.30
Purchase #4	$47.56	5.187%	$50.0269	$50.03	$50.05	$50.00
Purchase #5	$56.62	8.221%	$61.2747	$61.27	$61.25	$61.30
Purchase #6	$91.51	11.774%	$102.2844	$102.28	$102.30	$102.30
Purchase #7	$244.41	8.385%	$264.9038	$264.90	$264.90	$264.90
7 purchase totals =	$730.76		$801.5508	$801.54	$801.55	$801.60