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	$221.66	8.823%	$241.2171	$241.22	$241.20	$241.20
Purchase #2	$132.45	9.251%	$144.7029	$144.70	$144.70	$144.70
Purchase #3	$5.73	6.563%	$6.1061	$6.11	$6.10	$6.10
Purchase #4	$70.77	10.770%	$78.3919	$78.39	$78.40	$78.40
Purchase #5	$142.45	6.795%	$152.1295	$152.13	$152.15	$152.10
Purchase #6	$207.45	12.614%	$233.6177	$233.62	$233.60	$233.60
Purchase #7	$146.53	10.556%	$161.9977	$162.00	$162.00	$162.00
7 purchase totals =	$927.04		$1,018.1629	$1,018.17	$1,018.15	$1,018.10