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	$151.86	5.327%	$159.9496	$159.95	$159.95	$159.90
Purchase #2	$196.49	6.247%	$208.7647	$208.76	$208.75	$208.80
Purchase #3	$124.34	10.857%	$137.8396	$137.84	$137.85	$137.80
Purchase #4	$108.50	9.842%	$119.1786	$119.18	$119.20	$119.20
Purchase #5	$98.89	12.317%	$111.0703	$111.07	$111.05	$111.10
Purchase #6	$238.40	4.275%	$248.5916	$248.59	$248.60	$248.60
Purchase #7	$14.33	7.313%	$15.378	$15.38	$15.40	$15.40
7 purchase totals =	$932.81		$1,000.7724	$1,000.77	$1,000.80	$1,000.80