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	$119.80	6.513%	$127.6026	$127.60	$127.60	$127.60
Purchase #2	$87.56	13.507%	$99.3867	$99.39	$99.40	$99.40
Purchase #3	$217.97	10.671%	$241.2296	$241.23	$241.25	$241.20
Purchase #4	$189.26	5.780%	$200.1992	$200.20	$200.20	$200.20
Purchase #5	$168.90	10.390%	$186.4487	$186.45	$186.45	$186.40
Purchase #6	$111.56	4.298%	$116.3548	$116.35	$116.35	$116.40
Purchase #7	$129.89	3.259%	$134.1231	$134.12	$134.10	$134.10
7 purchase totals =	$1,024.94		$1,105.3447	$1,105.34	$1,105.35	$1,105.30