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	$6.83	10.741%	$7.5636	$7.56	$7.55	$7.60
Purchase #2	$214.42	5.212%	$225.5956	$225.60	$225.60	$225.60
Purchase #3	$193.64	8.739%	$210.5622	$210.56	$210.55	$210.60
Purchase #4	$112.72	12.230%	$126.5057	$126.51	$126.50	$126.50
Purchase #5	$61.39	7.114%	$65.7573	$65.76	$65.75	$65.80
Purchase #6	$7.61	10.173%	$8.3842	$8.38	$8.40	$8.40
Purchase #7	$29.42	11.777%	$32.8848	$32.88	$32.90	$32.90
7 purchase totals =	$626.03		$677.2534	$677.25	$677.25	$677.40