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	$248.43	11.409%	$276.7734	$276.77	$276.75	$276.80
Purchase #2	$101.41	9.573%	$111.118	$111.12	$111.10	$111.10
Purchase #3	$133.39	8.240%	$144.3813	$144.38	$144.40	$144.40
Purchase #4	$6.50	13.200%	$7.358	$7.36	$7.35	$7.40
Purchase #5	$193.90	8.435%	$210.2555	$210.26	$210.25	$210.30
Purchase #6	$161.66	6.539%	$172.2309	$172.23	$172.25	$172.20
Purchase #7	$204.95	8.126%	$221.6042	$221.60	$221.60	$221.60
7 purchase totals =	$1,050.24		$1,143.7213	$1,143.72	$1,143.70	$1,143.80