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	$89.52	4.587%	$93.6263	$93.63	$93.65	$93.60
Purchase #2	$228.44	8.827%	$248.6044	$248.60	$248.60	$248.60
Purchase #3	$35.95	3.687%	$37.2755	$37.28	$37.30	$37.30
Purchase #4	$33.49	6.272%	$35.5905	$35.59	$35.60	$35.60
Purchase #5	$223.34	10.773%	$247.4004	$247.40	$247.40	$247.40
Purchase #6	$164.45	10.562%	$181.8192	$181.82	$181.80	$181.80
Purchase #7	$192.43	6.835%	$205.5826	$205.58	$205.60	$205.60
7 purchase totals =	$967.62		$1,049.8989	$1,049.90	$1,049.95	$1,049.90