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	$176.42	12.568%	$198.5925	$198.59	$198.60	$198.60
Purchase #2	$181.55	6.210%	$192.8243	$192.82	$192.80	$192.80
Purchase #3	$129.40	12.450%	$145.5103	$145.51	$145.50	$145.50
Purchase #4	$205.60	10.492%	$227.1716	$227.17	$227.15	$227.20
Purchase #5	$166.74	3.296%	$172.2358	$172.24	$172.25	$172.20
Purchase #6	$10.94	5.580%	$11.5505	$11.55	$11.55	$11.60
Purchase #7	$158.81	8.637%	$172.5264	$172.53	$172.55	$172.50
7 purchase totals =	$1,029.46		$1,120.4114	$1,120.41	$1,120.40	$1,120.40