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	$205.28	3.728%	$212.9328	$212.93	$212.95	$212.90
Purchase #2	$131.39	12.794%	$148.2	$148.20	$148.20	$148.20
Purchase #3	$147.89	8.599%	$160.6071	$160.61	$160.60	$160.60
Purchase #4	$202.40	12.609%	$227.9206	$227.92	$227.90	$227.90
Purchase #5	$149.95	4.553%	$156.7772	$156.78	$156.80	$156.80
Purchase #6	$159.30	13.274%	$180.4455	$180.45	$180.45	$180.40
Purchase #7	$223.89	13.672%	$254.5002	$254.50	$254.50	$254.50
7 purchase totals =	$1,220.10		$1,341.3834	$1,341.39	$1,341.40	$1,341.30