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	$172.33	5.564%	$181.9184	$181.92	$181.90	$181.90
Purchase #2	$239.36	4.704%	$250.6195	$250.62	$250.60	$250.60
Purchase #3	$230.68	4.579%	$241.2428	$241.24	$241.25	$241.20
Purchase #4	$89.37	11.559%	$99.7003	$99.70	$99.70	$99.70
Purchase #5	$164.99	10.325%	$182.0252	$182.03	$182.05	$182.00
Purchase #6	$93.33	12.398%	$104.9011	$104.90	$104.90	$104.90
Purchase #7	$101.44	10.374%	$111.9634	$111.96	$111.95	$112.00
7 purchase totals =	$1,091.50		$1,172.3707	$1,172.37	$1,172.35	$1,172.30