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	$60.29	8.629%	$65.4924	$65.49	$65.50	$65.50
Purchase #2	$13.91	10.343%	$15.3487	$15.35	$15.35	$15.30
Purchase #3	$62.99	4.689%	$65.9436	$65.94	$65.95	$65.90
Purchase #4	$35.79	5.505%	$37.7602	$37.76	$37.75	$37.80
Purchase #5	$78.99	6.168%	$83.8621	$83.86	$83.85	$83.90
Purchase #6	$145.86	9.414%	$159.5913	$159.59	$159.60	$159.60
Purchase #7	$214.81	11.320%	$239.1265	$239.13	$239.15	$239.10
7 purchase totals =	$612.64		$667.1248	$667.12	$667.15	$667.10