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	$115.53	3.213%	$119.242	$119.24	$119.25	$119.20
Purchase #2	$68.86	13.237%	$77.975	$77.98	$78.00	$78.00
Purchase #3	$91.68	9.723%	$100.594	$100.59	$100.60	$100.60
Purchase #4	$168.99	5.639%	$178.5193	$178.52	$178.50	$178.50
Purchase #5	$72.89	13.571%	$82.7819	$82.78	$82.80	$82.80
Purchase #6	$138.96	10.142%	$153.0533	$153.05	$153.05	$153.10
Purchase #7	$249.34	10.191%	$274.7502	$274.75	$274.75	$274.80
7 purchase totals =	$906.25		$986.9157	$986.91	$986.95	$987.00