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	$41.54	11.403%	$46.2768	$46.28	$46.30	$46.30
Purchase #2	$40.51	7.487%	$43.543	$43.54	$43.55	$43.50
Purchase #3	$41.52	3.316%	$42.8968	$42.90	$42.90	$42.90
Purchase #4	$158.60	4.535%	$165.7925	$165.79	$165.80	$165.80
Purchase #5	$45.33	6.182%	$48.1323	$48.13	$48.15	$48.10
Purchase #6	$29.62	12.455%	$33.3092	$33.31	$33.30	$33.30
Purchase #7	$222.88	10.540%	$246.3716	$246.37	$246.35	$246.40
7 purchase totals =	$580.00		$626.3222	$626.32	$626.35	$626.30