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	$14.60	8.375%	$15.8228	$15.82	$15.80	$15.80
Purchase #2	$37.69	12.795%	$42.5124	$42.51	$42.50	$42.50
Purchase #3	$185.66	4.104%	$193.2795	$193.28	$193.30	$193.30
Purchase #4	$126.40	4.856%	$132.538	$132.54	$132.55	$132.50
Purchase #5	$139.72	6.436%	$148.7124	$148.71	$148.70	$148.70
Purchase #6	$151.75	5.628%	$160.2905	$160.29	$160.30	$160.30
Purchase #7	$244.91	5.805%	$259.127	$259.13	$259.15	$259.10
7 purchase totals =	$900.73		$952.2826	$952.28	$952.30	$952.20