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	$119.52	6.724%	$127.5565	$127.56	$127.55	$127.60
Purchase #2	$152.51	8.817%	$165.9568	$165.96	$165.95	$166.00
Purchase #3	$164.89	6.109%	$174.9631	$174.96	$174.95	$175.00
Purchase #4	$217.49	7.524%	$233.8539	$233.85	$233.85	$233.90
Purchase #5	$28.52	4.748%	$29.8741	$29.87	$29.85	$29.90
Purchase #6	$107.45	5.613%	$113.4812	$113.48	$113.50	$113.50
Purchase #7	$129.87	5.305%	$136.7596	$136.76	$136.75	$136.80
7 purchase totals =	$920.25		$982.4452	$982.44	$982.40	$982.70