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	$88.77	6.461%	$94.5054	$94.51	$94.50	$94.50
Purchase #2	$190.28	10.168%	$209.6277	$209.63	$209.65	$209.60
Purchase #3	$126.88	13.285%	$143.736	$143.74	$143.75	$143.70
Purchase #4	$219.47	8.852%	$238.8975	$238.90	$238.90	$238.90
Purchase #5	$244.65	4.348%	$255.2874	$255.29	$255.30	$255.30
Purchase #6	$70.42	11.539%	$78.5458	$78.55	$78.55	$78.50
Purchase #7	$130.67	4.714%	$136.8298	$136.83	$136.85	$136.80
7 purchase totals =	$1,071.14		$1,157.4296	$1,157.45	$1,157.50	$1,157.30