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	$237.27	7.754%	$255.6679	$255.67	$255.65	$255.70
Purchase #2	$71.61	9.366%	$78.317	$78.32	$78.30	$78.30
Purchase #3	$126.65	7.604%	$136.2805	$136.28	$136.30	$136.30
Purchase #4	$222.58	3.706%	$230.8288	$230.83	$230.85	$230.80
Purchase #5	$220.42	9.757%	$241.9264	$241.93	$241.95	$241.90
Purchase #6	$207.70	4.132%	$216.2822	$216.28	$216.30	$216.30
Purchase #7	$55.98	7.621%	$60.2462	$60.25	$60.25	$60.20
7 purchase totals =	$1,142.21		$1,219.5490	$1,219.56	$1,219.60	$1,219.50