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	$198.90	11.701%	$222.1733	$222.17	$222.15	$222.20
Purchase #2	$215.38	6.773%	$229.9677	$229.97	$229.95	$230.00
Purchase #3	$228.71	5.492%	$241.2708	$241.27	$241.25	$241.30
Purchase #4	$64.93	9.160%	$70.8776	$70.88	$70.90	$70.90
Purchase #5	$168.99	9.644%	$185.2874	$185.29	$185.30	$185.30
Purchase #6	$89.47	7.632%	$96.2984	$96.30	$96.30	$96.30
Purchase #7	$156.64	10.213%	$172.6376	$172.64	$172.65	$172.60
7 purchase totals =	$1,123.02		$1,218.5128	$1,218.52	$1,218.50	$1,218.60