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	$53.92	9.694%	$59.147	$59.15	$59.15	$59.10
Purchase #2	$40.55	4.559%	$42.3987	$42.40	$42.40	$42.40
Purchase #3	$85.25	6.250%	$90.5781	$90.58	$90.60	$90.60
Purchase #4	$246.44	4.341%	$257.138	$257.14	$257.15	$257.10
Purchase #5	$232.44	4.202%	$242.2071	$242.21	$242.20	$242.20
Purchase #6	$112.82	4.309%	$117.6814	$117.68	$117.70	$117.70
Purchase #7	$142.95	7.468%	$153.6255	$153.63	$153.65	$153.60
7 purchase totals =	$914.37		$962.7758	$962.79	$962.85	$962.70