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	$206.95	3.834%	$214.8845	$214.88	$214.90	$214.90
Purchase #2	$138.75	11.309%	$154.4412	$154.44	$154.45	$154.40
Purchase #3	$72.94	13.275%	$82.6228	$82.62	$82.60	$82.60
Purchase #4	$132.87	10.539%	$146.8732	$146.87	$146.85	$146.90
Purchase #5	$19.54	11.196%	$21.7277	$21.73	$21.75	$21.70
Purchase #6	$58.87	13.235%	$66.6614	$66.66	$66.65	$66.70
Purchase #7	$148.35	11.672%	$165.6654	$165.67	$165.65	$165.70
7 purchase totals =	$778.27		$852.8762	$852.87	$852.85	$852.90