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	$60.32	3.341%	$62.3353	$62.34	$62.35	$62.30
Purchase #2	$124.65	5.362%	$131.3337	$131.33	$131.35	$131.30
Purchase #3	$54.54	11.554%	$60.8416	$60.84	$60.85	$60.80
Purchase #4	$16.95	8.788%	$18.4396	$18.44	$18.45	$18.40
Purchase #5	$188.72	11.727%	$210.8512	$210.85	$210.85	$210.90
Purchase #6	$21.74	10.789%	$24.0855	$24.09	$24.10	$24.10
Purchase #7	$243.75	4.773%	$255.3842	$255.38	$255.40	$255.40
7 purchase totals =	$710.67		$763.2711	$763.27	$763.35	$763.20