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	$89.42	9.412%	$97.8362	$97.84	$97.85	$97.80
Purchase #2	$136.39	12.156%	$152.9696	$152.97	$152.95	$153.00
Purchase #3	$99.97	11.549%	$111.5155	$111.52	$111.50	$111.50
Purchase #4	$122.28	6.578%	$130.3236	$130.32	$130.30	$130.30
Purchase #5	$102.39	9.301%	$111.9133	$111.91	$111.90	$111.90
Purchase #6	$220.65	3.453%	$228.269	$228.27	$228.25	$228.30
Purchase #7	$18.99	11.455%	$21.1653	$21.17	$21.15	$21.20
7 purchase totals =	$790.09		$853.9925	$854.00	$853.90	$854.00