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	$53.89	5.131%	$56.6551	$56.66	$56.65	$56.70
Purchase #2	$160.75	4.405%	$167.831	$167.83	$167.85	$167.80
Purchase #3	$56.83	10.132%	$62.588	$62.59	$62.60	$62.60
Purchase #4	$46.53	8.835%	$50.6409	$50.64	$50.65	$50.60
Purchase #5	$174.75	10.191%	$192.5588	$192.56	$192.55	$192.60
Purchase #6	$44.42	13.148%	$50.2603	$50.26	$50.25	$50.30
Purchase #7	$31.40	5.241%	$33.0457	$33.05	$33.05	$33.00
7 purchase totals =	$568.57		$613.5798	$613.59	$613.60	$613.60