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	$149.58	9.681%	$164.0608	$164.06	$164.05	$164.10
Purchase #2	$147.81	7.201%	$158.4538	$158.45	$158.45	$158.50
Purchase #3	$139.89	3.806%	$145.2142	$145.21	$145.20	$145.20
Purchase #4	$146.44	13.310%	$165.9312	$165.93	$165.95	$165.90
Purchase #5	$143.40	11.421%	$159.7777	$159.78	$159.80	$159.80
Purchase #6	$121.83	13.201%	$137.9128	$137.91	$137.90	$137.90
Purchase #7	$90.42	5.536%	$95.4257	$95.43	$95.45	$95.40
7 purchase totals =	$939.37		$1,026.7762	$1,026.77	$1,026.80	$1,026.80