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	$84.72	13.387%	$96.0615	$96.06	$96.05	$96.10
Purchase #2	$27.50	11.402%	$30.6356	$30.64	$30.65	$30.60
Purchase #3	$132.51	9.627%	$145.2667	$145.27	$145.25	$145.30
Purchase #4	$29.42	10.747%	$32.5818	$32.58	$32.60	$32.60
Purchase #5	$184.78	6.180%	$196.1994	$196.20	$196.20	$196.20
Purchase #6	$34.59	3.159%	$35.6827	$35.68	$35.70	$35.70
Purchase #7	$37.94	5.632%	$40.0768	$40.08	$40.10	$40.10
7 purchase totals =	$531.46		$576.5045	$576.51	$576.55	$576.60