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	$10.81	8.329%	$11.7104	$11.71	$11.70	$11.70
Purchase #2	$34.83	6.548%	$37.1107	$37.11	$37.10	$37.10
Purchase #3	$139.47	12.469%	$156.8605	$156.86	$156.85	$156.90
Purchase #4	$69.89	5.537%	$73.7598	$73.76	$73.75	$73.80
Purchase #5	$18.69	8.733%	$20.3222	$20.32	$20.30	$20.30
Purchase #6	$111.49	4.812%	$116.8549	$116.85	$116.85	$116.90
Purchase #7	$29.58	7.522%	$31.805	$31.81	$31.80	$31.80
7 purchase totals =	$414.76		$448.4235	$448.42	$448.35	$448.50