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	$103.32	8.324%	$111.9204	$111.92	$111.90	$111.90
Purchase #2	$70.59	4.550%	$73.8018	$73.80	$73.80	$73.80
Purchase #3	$107.53	7.490%	$115.584	$115.58	$115.60	$115.60
Purchase #4	$53.80	5.770%	$56.9043	$56.90	$56.90	$56.90
Purchase #5	$82.30	8.427%	$89.2354	$89.24	$89.25	$89.20
Purchase #6	$136.43	5.722%	$144.2365	$144.24	$144.25	$144.20
Purchase #7	$250.66	10.293%	$276.4604	$276.46	$276.45	$276.50
7 purchase totals =	$804.63		$868.1428	$868.14	$868.15	$868.10