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	$213.98	13.476%	$242.8159	$242.82	$242.80	$242.80
Purchase #2	$93.44	7.154%	$100.1247	$100.12	$100.10	$100.10
Purchase #3	$163.39	10.506%	$180.5558	$180.56	$180.55	$180.60
Purchase #4	$54.29	3.631%	$56.2613	$56.26	$56.25	$56.30
Purchase #5	$118.30	13.523%	$134.2977	$134.30	$134.30	$134.30
Purchase #6	$139.42	10.177%	$153.6088	$153.61	$153.60	$153.60
Purchase #7	$160.95	4.706%	$168.5243	$168.52	$168.50	$168.50
7 purchase totals =	$943.77		$1,036.1885	$1,036.19	$1,036.10	$1,036.20