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	$168.56	10.159%	$185.684	$185.68	$185.70	$185.70
Purchase #2	$144.60	8.808%	$157.3364	$157.34	$157.35	$157.30
Purchase #3	$189.30	8.501%	$205.3924	$205.39	$205.40	$205.40
Purchase #4	$153.58	7.811%	$165.5761	$165.58	$165.60	$165.60
Purchase #5	$155.50	3.425%	$160.8259	$160.83	$160.85	$160.80
Purchase #6	$32.69	3.132%	$33.7139	$33.71	$33.70	$33.70
Purchase #7	$151.59	13.734%	$172.4094	$172.41	$172.40	$172.40
7 purchase totals =	$995.82		$1,080.9381	$1,080.94	$1,081.00	$1,080.90