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	$117.86	13.714%	$134.0233	$134.02	$134.00	$134.00
Purchase #2	$99.92	11.469%	$111.3798	$111.38	$111.40	$111.40
Purchase #3	$101.89	7.540%	$109.5725	$109.57	$109.55	$109.60
Purchase #4	$100.69	7.517%	$108.2589	$108.26	$108.25	$108.30
Purchase #5	$247.37	11.505%	$275.8299	$275.83	$275.85	$275.80
Purchase #6	$16.51	10.185%	$18.1915	$18.19	$18.20	$18.20
Purchase #7	$18.51	3.129%	$19.0892	$19.09	$19.10	$19.10
7 purchase totals =	$702.75		$776.3451	$776.34	$776.35	$776.40