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	$210.92	5.353%	$222.2105	$222.21	$222.20	$222.20
Purchase #2	$114.40	11.732%	$127.8214	$127.82	$127.80	$127.80
Purchase #3	$157.69	9.251%	$172.2779	$172.28	$172.30	$172.30
Purchase #4	$217.99	10.109%	$240.0266	$240.03	$240.05	$240.00
Purchase #5	$222.72	4.771%	$233.346	$233.35	$233.35	$233.30
Purchase #6	$201.54	13.599%	$228.9474	$228.95	$228.95	$228.90
Purchase #7	$38.86	9.429%	$42.5241	$42.52	$42.50	$42.50
7 purchase totals =	$1,164.12		$1,267.1539	$1,267.16	$1,267.15	$1,267.00