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	$221.26	11.414%	$246.5146	$246.51	$246.50	$246.50
Purchase #2	$164.79	10.615%	$182.2825	$182.28	$182.30	$182.30
Purchase #3	$130.43	11.307%	$145.1777	$145.18	$145.20	$145.20
Purchase #4	$205.72	5.440%	$216.9112	$216.91	$216.90	$216.90
Purchase #5	$137.91	7.749%	$148.5966	$148.60	$148.60	$148.60
Purchase #6	$92.84	8.302%	$100.5476	$100.55	$100.55	$100.50
Purchase #7	$213.97	13.527%	$242.9137	$242.91	$242.90	$242.90
7 purchase totals =	$1,166.92		$1,282.9439	$1,282.94	$1,282.95	$1,282.90