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	$146.37	4.228%	$152.5585	$152.56	$152.55	$152.60
Purchase #2	$131.89	9.149%	$143.9566	$143.96	$143.95	$144.00
Purchase #3	$48.87	11.722%	$54.5985	$54.60	$54.60	$54.60
Purchase #4	$27.55	8.715%	$29.951	$29.95	$29.95	$30.00
Purchase #5	$149.69	11.864%	$167.4492	$167.45	$167.45	$167.40
Purchase #6	$78.61	3.864%	$81.6475	$81.65	$81.65	$81.60
Purchase #7	$101.56	3.311%	$104.9227	$104.92	$104.90	$104.90
7 purchase totals =	$684.54		$735.0840	$735.09	$735.05	$735.10