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	$143.89	6.628%	$153.427	$153.43	$153.45	$153.40
Purchase #2	$224.46	4.620%	$234.8301	$234.83	$234.85	$234.80
Purchase #3	$52.31	4.412%	$54.6179	$54.62	$54.60	$54.60
Purchase #4	$135.76	7.616%	$146.0995	$146.10	$146.10	$146.10
Purchase #5	$76.66	7.858%	$82.6839	$82.68	$82.70	$82.70
Purchase #6	$90.97	9.198%	$99.3374	$99.34	$99.35	$99.30
Purchase #7	$92.42	11.725%	$103.2562	$103.26	$103.25	$103.30
7 purchase totals =	$816.47		$874.2520	$874.26	$874.30	$874.20