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	$75.42	4.670%	$78.9421	$78.94	$78.95	$78.90
Purchase #2	$67.82	8.224%	$73.3975	$73.40	$73.40	$73.40
Purchase #3	$233.57	12.431%	$262.6051	$262.61	$262.60	$262.60
Purchase #4	$239.61	6.679%	$255.6136	$255.61	$255.60	$255.60
Purchase #5	$101.96	9.624%	$111.7726	$111.77	$111.75	$111.80
Purchase #6	$220.57	5.181%	$231.9977	$232.00	$232.00	$232.00
Purchase #7	$105.82	12.214%	$118.7449	$118.74	$118.75	$118.70
7 purchase totals =	$1,044.77		$1,133.0735	$1,133.07	$1,133.05	$1,133.00