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	$49.55	9.480%	$54.2473	$54.25	$54.25	$54.20
Purchase #2	$57.31	6.525%	$61.0495	$61.05	$61.05	$61.00
Purchase #3	$159.45	4.596%	$166.7783	$166.78	$166.80	$166.80
Purchase #4	$206.83	4.158%	$215.43	$215.43	$215.45	$215.40
Purchase #5	$204.77	4.761%	$214.5191	$214.52	$214.50	$214.50
Purchase #6	$42.66	3.429%	$44.1228	$44.12	$44.10	$44.10
Purchase #7	$162.51	13.531%	$184.4992	$184.50	$184.50	$184.50
7 purchase totals =	$883.08		$940.6462	$940.65	$940.65	$940.50