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	$196.54	8.548%	$213.3402	$213.34	$213.35	$213.30
Purchase #2	$164.25	8.662%	$178.4773	$178.48	$178.50	$178.50
Purchase #3	$78.67	9.151%	$85.8691	$85.87	$85.85	$85.90
Purchase #4	$32.50	10.145%	$35.7971	$35.80	$35.80	$35.80
Purchase #5	$132.82	13.806%	$151.1571	$151.16	$151.15	$151.20
Purchase #6	$191.54	7.191%	$205.3136	$205.31	$205.30	$205.30
Purchase #7	$19.59	9.332%	$21.4181	$21.42	$21.40	$21.40
7 purchase totals =	$815.91		$891.3725	$891.38	$891.35	$891.40