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	$38.84	6.756%	$41.464	$41.46	$41.45	$41.50
Purchase #2	$93.30	11.109%	$103.6647	$103.66	$103.65	$103.70
Purchase #3	$149.72	8.640%	$162.6558	$162.66	$162.65	$162.70
Purchase #4	$167.52	12.285%	$188.0998	$188.10	$188.10	$188.10
Purchase #5	$129.86	10.772%	$143.8485	$143.85	$143.85	$143.80
Purchase #6	$33.49	11.810%	$37.4452	$37.45	$37.45	$37.40
Purchase #7	$205.75	5.573%	$217.2164	$217.22	$217.20	$217.20
7 purchase totals =	$818.48		$894.3944	$894.40	$894.35	$894.40