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	$143.43	11.571%	$160.0263	$160.03	$160.05	$160.00
Purchase #2	$81.58	7.665%	$87.8331	$87.83	$87.85	$87.80
Purchase #3	$166.25	3.690%	$172.3846	$172.38	$172.40	$172.40
Purchase #4	$106.32	5.708%	$112.3887	$112.39	$112.40	$112.40
Purchase #5	$146.31	3.546%	$151.4982	$151.50	$151.50	$151.50
Purchase #6	$6.51	6.708%	$6.9467	$6.95	$6.95	$6.90
Purchase #7	$245.92	3.339%	$254.1313	$254.13	$254.15	$254.10
7 purchase totals =	$896.32		$945.2089	$945.21	$945.30	$945.10