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	$33.37	13.452%	$37.8589	$37.86	$37.85	$37.90
Purchase #2	$207.73	5.402%	$218.9516	$218.95	$218.95	$219.00
Purchase #3	$107.47	3.585%	$111.3228	$111.32	$111.30	$111.30
Purchase #4	$10.26	3.476%	$10.6166	$10.62	$10.60	$10.60
Purchase #5	$225.67	13.108%	$255.2508	$255.25	$255.25	$255.30
Purchase #6	$159.58	4.287%	$166.4212	$166.42	$166.40	$166.40
Purchase #7	$16.76	10.127%	$18.4573	$18.46	$18.45	$18.50
7 purchase totals =	$760.84		$818.8792	$818.88	$818.80	$819.00