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	$33.51	10.724%	$37.1036	$37.10	$37.10	$37.10
Purchase #2	$56.58	10.831%	$62.7082	$62.71	$62.70	$62.70
Purchase #3	$153.76	12.393%	$172.8155	$172.82	$172.80	$172.80
Purchase #4	$60.79	7.675%	$65.4556	$65.46	$65.45	$65.50
Purchase #5	$18.83	8.273%	$20.3878	$20.39	$20.40	$20.40
Purchase #6	$144.79	6.498%	$154.1985	$154.20	$154.20	$154.20
Purchase #7	$101.30	10.871%	$112.3123	$112.31	$112.30	$112.30
7 purchase totals =	$569.56		$624.9815	$624.99	$624.95	$625.00