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	$174.41	10.284%	$192.3463	$192.35	$192.35	$192.30
Purchase #2	$240.31	5.601%	$253.7698	$253.77	$253.75	$253.80
Purchase #3	$83.81	10.482%	$92.595	$92.60	$92.60	$92.60
Purchase #4	$146.28	5.577%	$154.438	$154.44	$154.45	$154.40
Purchase #5	$160.78	4.650%	$168.2563	$168.26	$168.25	$168.30
Purchase #6	$18.42	6.448%	$19.6077	$19.61	$19.60	$19.60
Purchase #7	$214.85	6.342%	$228.4758	$228.48	$228.50	$228.50
7 purchase totals =	$1,038.86		$1,109.4889	$1,109.51	$1,109.50	$1,109.50