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	$148.52	3.317%	$153.4464	$153.45	$153.45	$153.40
Purchase #2	$71.77	9.259%	$78.4152	$78.42	$78.40	$78.40
Purchase #3	$182.51	5.466%	$192.486	$192.49	$192.50	$192.50
Purchase #4	$239.66	6.412%	$255.027	$255.03	$255.05	$255.00
Purchase #5	$38.60	7.612%	$41.5382	$41.54	$41.55	$41.50
Purchase #6	$141.60	7.844%	$152.7071	$152.71	$152.70	$152.70
Purchase #7	$107.90	11.552%	$120.3646	$120.36	$120.35	$120.40
7 purchase totals =	$930.56		$993.9845	$994.00	$994.00	$993.90