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	$125.68	4.499%	$131.3343	$131.33	$131.35	$131.30
Purchase #2	$100.79	6.612%	$107.4542	$107.45	$107.45	$107.50
Purchase #3	$8.82	10.574%	$9.7526	$9.75	$9.75	$9.80
Purchase #4	$132.89	9.150%	$145.0494	$145.05	$145.05	$145.00
Purchase #5	$43.64	4.154%	$45.4528	$45.45	$45.45	$45.50
Purchase #6	$223.54	13.665%	$254.0867	$254.09	$254.10	$254.10
Purchase #7	$158.32	8.817%	$172.2791	$172.28	$172.30	$172.30
7 purchase totals =	$793.68		$865.4091	$865.40	$865.45	$865.50