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	$248.75	4.102%	$258.9537	$258.95	$258.95	$259.00
Purchase #2	$42.62	9.557%	$46.6932	$46.69	$46.70	$46.70
Purchase #3	$162.89	6.609%	$173.6554	$173.66	$173.65	$173.70
Purchase #4	$172.90	13.564%	$196.3522	$196.35	$196.35	$196.40
Purchase #5	$149.52	9.791%	$164.1595	$164.16	$164.15	$164.20
Purchase #6	$61.37	8.673%	$66.6926	$66.69	$66.70	$66.70
Purchase #7	$52.56	8.110%	$56.8226	$56.82	$56.80	$56.80
7 purchase totals =	$890.61		$963.3292	$963.32	$963.30	$963.50