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	$14.49	5.858%	$15.3388	$15.34	$15.35	$15.30
Purchase #2	$90.52	5.280%	$95.2995	$95.30	$95.30	$95.30
Purchase #3	$147.37	12.572%	$165.8974	$165.90	$165.90	$165.90
Purchase #4	$48.56	8.835%	$52.8503	$52.85	$52.85	$52.90
Purchase #5	$167.66	13.374%	$190.0828	$190.08	$190.10	$190.10
Purchase #6	$150.25	11.237%	$167.1336	$167.13	$167.15	$167.10
Purchase #7	$62.38	6.103%	$66.1871	$66.19	$66.20	$66.20
7 purchase totals =	$681.23		$752.7895	$752.79	$752.85	$752.80