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	$184.83	6.530%	$196.8994	$196.90	$196.90	$196.90
Purchase #2	$94.37	10.803%	$104.5648	$104.56	$104.55	$104.60
Purchase #3	$185.63	10.618%	$205.3402	$205.34	$205.35	$205.30
Purchase #4	$111.58	13.813%	$126.9925	$126.99	$127.00	$127.00
Purchase #5	$60.55	13.113%	$68.4899	$68.49	$68.50	$68.50
Purchase #6	$29.71	13.111%	$33.6053	$33.61	$33.60	$33.60
Purchase #7	$69.42	7.377%	$74.5411	$74.54	$74.55	$74.50
7 purchase totals =	$736.09		$810.4332	$810.43	$810.45	$810.40