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	$55.52	6.191%	$58.9572	$58.96	$58.95	$59.00
Purchase #2	$216.63	13.136%	$245.0865	$245.09	$245.10	$245.10
Purchase #3	$180.62	5.140%	$189.9039	$189.90	$189.90	$189.90
Purchase #4	$151.89	10.180%	$167.3524	$167.35	$167.35	$167.40
Purchase #5	$10.63	4.806%	$11.1409	$11.14	$11.15	$11.10
Purchase #6	$92.92	11.503%	$103.6086	$103.61	$103.60	$103.60
Purchase #7	$139.94	8.622%	$152.0056	$152.01	$152.00	$152.00
7 purchase totals =	$848.15		$928.0551	$928.06	$928.05	$928.10