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	$176.61	5.688%	$186.6556	$186.66	$186.65	$186.70
Purchase #2	$7.68	10.395%	$8.4783	$8.48	$8.50	$8.50
Purchase #3	$157.31	7.384%	$168.9258	$168.93	$168.95	$168.90
Purchase #4	$99.48	12.227%	$111.6434	$111.64	$111.65	$111.60
Purchase #5	$30.78	3.580%	$31.8819	$31.88	$31.90	$31.90
Purchase #6	$11.73	6.497%	$12.4921	$12.49	$12.50	$12.50
Purchase #7	$117.58	7.422%	$126.3068	$126.31	$126.30	$126.30
7 purchase totals =	$601.17		$646.3839	$646.39	$646.45	$646.40