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	$111.65	4.239%	$116.3828	$116.38	$116.40	$116.40
Purchase #2	$108.53	5.634%	$114.6446	$114.64	$114.65	$114.60
Purchase #3	$60.96	10.643%	$67.448	$67.45	$67.45	$67.40
Purchase #4	$37.42	8.279%	$40.518	$40.52	$40.50	$40.50
Purchase #5	$20.49	10.751%	$22.6929	$22.69	$22.70	$22.70
Purchase #6	$176.90	5.869%	$187.2823	$187.28	$187.30	$187.30
Purchase #7	$151.38	3.377%	$156.4921	$156.49	$156.50	$156.50
7 purchase totals =	$667.33		$705.4607	$705.45	$705.50	$705.40