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	$109.56	8.261%	$118.6108	$118.61	$118.60	$118.60
Purchase #2	$88.46	5.178%	$93.0405	$93.04	$93.05	$93.00
Purchase #3	$141.75	11.138%	$157.5381	$157.54	$157.55	$157.50
Purchase #4	$241.87	5.558%	$255.3131	$255.31	$255.30	$255.30
Purchase #5	$211.49	3.812%	$219.552	$219.55	$219.55	$219.60
Purchase #6	$105.58	5.438%	$111.3214	$111.32	$111.30	$111.30
Purchase #7	$193.61	8.109%	$209.3098	$209.31	$209.30	$209.30
7 purchase totals =	$1,092.32		$1,164.6857	$1,164.68	$1,164.65	$1,164.60