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	$102.95	5.543%	$108.6565	$108.66	$108.65	$108.70
Purchase #2	$155.55	3.437%	$160.8963	$160.90	$160.90	$160.90
Purchase #3	$33.89	11.567%	$37.8101	$37.81	$37.80	$37.80
Purchase #4	$58.71	13.169%	$66.4415	$66.44	$66.45	$66.40
Purchase #5	$193.44	12.259%	$217.1538	$217.15	$217.15	$217.20
Purchase #6	$39.43	7.870%	$42.5331	$42.53	$42.55	$42.50
Purchase #7	$118.43	7.602%	$127.433	$127.43	$127.45	$127.40
7 purchase totals =	$702.40		$760.9243	$760.92	$760.95	$760.90