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	$179.32	8.424%	$194.4259	$194.43	$194.45	$194.40
Purchase #2	$59.62	10.639%	$65.963	$65.96	$65.95	$66.00
Purchase #3	$94.78	6.449%	$100.8924	$100.89	$100.90	$100.90
Purchase #4	$15.86	7.607%	$17.0665	$17.07	$17.05	$17.10
Purchase #5	$14.92	10.531%	$16.4912	$16.49	$16.50	$16.50
Purchase #6	$132.90	13.446%	$150.7697	$150.77	$150.75	$150.80
Purchase #7	$231.65	10.474%	$255.913	$255.91	$255.90	$255.90
7 purchase totals =	$729.05		$801.5217	$801.52	$801.50	$801.60