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	$162.56	8.782%	$176.836	$176.84	$176.85	$176.80
Purchase #2	$88.28	13.615%	$100.2993	$100.30	$100.30	$100.30
Purchase #3	$91.83	13.518%	$104.2436	$104.24	$104.25	$104.20
Purchase #4	$148.90	7.398%	$159.9156	$159.92	$159.90	$159.90
Purchase #5	$42.93	3.212%	$44.3089	$44.31	$44.30	$44.30
Purchase #6	$44.71	9.489%	$48.9525	$48.95	$48.95	$49.00
Purchase #7	$153.56	12.401%	$172.603	$172.60	$172.60	$172.60
7 purchase totals =	$732.77		$807.1589	$807.16	$807.15	$807.10