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	$37.81	13.671%	$42.979	$42.98	$43.00	$43.00
Purchase #2	$56.92	13.835%	$64.7949	$64.79	$64.80	$64.80
Purchase #3	$163.66	5.432%	$172.55	$172.55	$172.55	$172.60
Purchase #4	$120.95	5.145%	$127.1729	$127.17	$127.15	$127.20
Purchase #5	$146.72	8.259%	$158.8376	$158.84	$158.85	$158.80
Purchase #6	$208.81	10.699%	$231.1506	$231.15	$231.15	$231.20
Purchase #7	$171.38	10.854%	$189.9816	$189.98	$190.00	$190.00
7 purchase totals =	$906.25		$987.4666	$987.46	$987.50	$987.60