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	$221.53	7.280%	$237.6574	$237.66	$237.65	$237.70
Purchase #2	$35.65	5.466%	$37.5986	$37.60	$37.60	$37.60
Purchase #3	$211.39	5.103%	$222.1772	$222.18	$222.20	$222.20
Purchase #4	$104.41	13.144%	$118.1337	$118.13	$118.15	$118.10
Purchase #5	$209.83	13.463%	$238.0794	$238.08	$238.10	$238.10
Purchase #6	$202.83	10.838%	$224.8127	$224.81	$224.80	$224.80
Purchase #7	$179.51	8.123%	$194.0916	$194.09	$194.10	$194.10
7 purchase totals =	$1,165.15		$1,272.5506	$1,272.55	$1,272.60	$1,272.60