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	$64.92	10.225%	$71.5581	$71.56	$71.55	$71.60
Purchase #2	$112.60	13.199%	$127.4621	$127.46	$127.45	$127.50
Purchase #3	$164.64	5.172%	$173.1552	$173.16	$173.15	$173.20
Purchase #4	$138.54	7.209%	$148.5273	$148.53	$148.55	$148.50
Purchase #5	$210.28	3.748%	$218.1613	$218.16	$218.15	$218.20
Purchase #6	$160.66	12.291%	$180.4067	$180.41	$180.40	$180.40
Purchase #7	$153.59	13.425%	$174.2095	$174.21	$174.20	$174.20
7 purchase totals =	$1,005.23		$1,093.4802	$1,093.49	$1,093.45	$1,093.60