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	$76.60	7.645%	$82.4561	$82.46	$82.45	$82.50
Purchase #2	$120.67	8.439%	$130.8533	$130.85	$130.85	$130.90
Purchase #3	$94.86	4.767%	$99.382	$99.38	$99.40	$99.40
Purchase #4	$227.62	12.860%	$256.8919	$256.89	$256.90	$256.90
Purchase #5	$26.59	9.672%	$29.1618	$29.16	$29.15	$29.20
Purchase #6	$247.25	12.434%	$277.9931	$277.99	$278.00	$278.00
Purchase #7	$107.64	3.635%	$111.5527	$111.55	$111.55	$111.60
7 purchase totals =	$901.23		$988.2909	$988.28	$988.30	$988.50