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	$88.45	11.295%	$98.4404	$98.44	$98.45	$98.40
Purchase #2	$230.76	4.617%	$241.4142	$241.41	$241.40	$241.40
Purchase #3	$244.66	11.244%	$272.1696	$272.17	$272.15	$272.20
Purchase #4	$159.76	4.166%	$166.4156	$166.42	$166.40	$166.40
Purchase #5	$148.83	7.832%	$160.4864	$160.49	$160.50	$160.50
Purchase #6	$89.40	5.814%	$94.5977	$94.60	$94.60	$94.60
Purchase #7	$37.74	10.774%	$41.8061	$41.81	$41.80	$41.80
7 purchase totals =	$999.60		$1,075.3300	$1,075.34	$1,075.30	$1,075.30