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	$45.77	5.826%	$48.4366	$48.44	$48.45	$48.40
Purchase #2	$31.98	8.162%	$34.5902	$34.59	$34.60	$34.60
Purchase #3	$99.92	11.106%	$111.0171	$111.02	$111.00	$111.00
Purchase #4	$158.44	8.812%	$172.4017	$172.40	$172.40	$172.40
Purchase #5	$152.74	9.349%	$167.0197	$167.02	$167.00	$167.00
Purchase #6	$84.30	7.251%	$90.4126	$90.41	$90.40	$90.40
Purchase #7	$31.28	10.840%	$34.6708	$34.67	$34.65	$34.70
7 purchase totals =	$604.43		$658.5487	$658.55	$658.50	$658.50