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	$163.88	5.233%	$172.4558	$172.46	$172.45	$172.50
Purchase #2	$165.56	12.350%	$186.0067	$186.01	$186.00	$186.00
Purchase #3	$136.90	11.612%	$152.7968	$152.80	$152.80	$152.80
Purchase #4	$222.92	13.486%	$252.983	$252.98	$253.00	$253.00
Purchase #5	$94.35	7.694%	$101.6093	$101.61	$101.60	$101.60
Purchase #6	$68.66	8.820%	$74.7158	$74.72	$74.70	$74.70
Purchase #7	$225.92	13.230%	$255.8092	$255.81	$255.80	$255.80
7 purchase totals =	$1,078.19		$1,196.3766	$1,196.39	$1,196.35	$1,196.40