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	$49.56	11.846%	$55.4309	$55.43	$55.45	$55.40
Purchase #2	$102.67	5.245%	$108.055	$108.06	$108.05	$108.10
Purchase #3	$178.95	4.374%	$186.7773	$186.78	$186.80	$186.80
Purchase #4	$83.45	8.801%	$90.7944	$90.79	$90.80	$90.80
Purchase #5	$111.75	13.843%	$127.2196	$127.22	$127.20	$127.20
Purchase #6	$243.85	4.819%	$255.6011	$255.60	$255.60	$255.60
Purchase #7	$146.51	10.605%	$162.0474	$162.05	$162.05	$162.00
7 purchase totals =	$916.74		$985.9257	$985.93	$985.95	$985.90