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	$215.53	10.204%	$237.5227	$237.52	$237.50	$237.50
Purchase #2	$238.83	6.780%	$255.0227	$255.02	$255.00	$255.00
Purchase #3	$123.85	4.130%	$128.965	$128.97	$128.95	$129.00
Purchase #4	$18.83	9.111%	$20.5456	$20.55	$20.55	$20.50
Purchase #5	$155.80	3.787%	$161.7001	$161.70	$161.70	$161.70
Purchase #6	$40.36	4.435%	$42.15	$42.15	$42.15	$42.20
Purchase #7	$157.43	9.627%	$172.5858	$172.59	$172.60	$172.60
7 purchase totals =	$950.63		$1,018.4919	$1,018.50	$1,018.45	$1,018.50