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	$99.43	11.607%	$110.9708	$110.97	$110.95	$111.00
Purchase #2	$205.25	5.102%	$215.7219	$215.72	$215.70	$215.70
Purchase #3	$150.89	13.179%	$170.7758	$170.78	$170.80	$170.80
Purchase #4	$146.93	8.178%	$158.9459	$158.95	$158.95	$158.90
Purchase #5	$45.28	5.640%	$47.8338	$47.83	$47.85	$47.80
Purchase #6	$17.34	4.606%	$18.1387	$18.14	$18.15	$18.10
Purchase #7	$52.58	13.248%	$59.5458	$59.55	$59.55	$59.50
7 purchase totals =	$717.70		$781.9327	$781.94	$781.95	$781.80