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	$35.63	11.420%	$39.6989	$39.70	$39.70	$39.70
Purchase #2	$89.31	11.576%	$99.6485	$99.65	$99.65	$99.60
Purchase #3	$12.67	11.455%	$14.1213	$14.12	$14.10	$14.10
Purchase #4	$13.48	10.828%	$14.9396	$14.94	$14.95	$14.90
Purchase #5	$143.42	6.555%	$152.8212	$152.82	$152.80	$152.80
Purchase #6	$44.87	8.147%	$48.5256	$48.53	$48.55	$48.50
Purchase #7	$123.32	3.513%	$127.6522	$127.65	$127.65	$127.70
7 purchase totals =	$462.70		$497.4073	$497.41	$497.40	$497.30