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	$246.46	10.306%	$271.8602	$271.86	$271.85	$271.90
Purchase #2	$91.76	8.526%	$99.5835	$99.58	$99.60	$99.60
Purchase #3	$94.55	11.178%	$105.1188	$105.12	$105.10	$105.10
Purchase #4	$148.52	11.432%	$165.4988	$165.50	$165.50	$165.50
Purchase #5	$214.60	9.704%	$235.4248	$235.42	$235.40	$235.40
Purchase #6	$91.69	8.738%	$99.7019	$99.70	$99.70	$99.70
Purchase #7	$143.55	8.170%	$155.278	$155.28	$155.30	$155.30
7 purchase totals =	$1,031.13		$1,132.4660	$1,132.46	$1,132.45	$1,132.50