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	$63.89	13.506%	$72.519	$72.52	$72.50	$72.50
Purchase #2	$105.75	3.480%	$109.4301	$109.43	$109.45	$109.40
Purchase #3	$174.67	8.106%	$188.8288	$188.83	$188.85	$188.80
Purchase #4	$72.80	6.239%	$77.342	$77.34	$77.35	$77.30
Purchase #5	$202.78	5.869%	$214.6812	$214.68	$214.70	$214.70
Purchase #6	$169.57	10.644%	$187.619	$187.62	$187.60	$187.60
Purchase #7	$245.94	7.102%	$263.4067	$263.41	$263.40	$263.40
7 purchase totals =	$1,035.40		$1,113.8268	$1,113.83	$1,113.85	$1,113.70