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	$94.94	13.563%	$107.8167	$107.82	$107.80	$107.80
Purchase #2	$54.73	5.104%	$57.5234	$57.52	$57.50	$57.50
Purchase #3	$180.50	5.491%	$190.4113	$190.41	$190.40	$190.40
Purchase #4	$89.49	13.330%	$101.419	$101.42	$101.40	$101.40
Purchase #5	$65.77	3.657%	$68.1752	$68.18	$68.20	$68.20
Purchase #6	$36.97	8.617%	$40.1557	$40.16	$40.15	$40.20
Purchase #7	$180.63	11.185%	$200.8335	$200.83	$200.85	$200.80
7 purchase totals =	$703.03		$766.3348	$766.34	$766.30	$766.30