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	$10.55	8.121%	$11.4068	$11.41	$11.40	$11.40
Purchase #2	$134.31	12.168%	$150.6528	$150.65	$150.65	$150.70
Purchase #3	$90.68	13.389%	$102.8211	$102.82	$102.80	$102.80
Purchase #4	$223.87	13.327%	$253.7052	$253.71	$253.70	$253.70
Purchase #5	$222.97	10.110%	$245.5123	$245.51	$245.50	$245.50
Purchase #6	$237.86	7.278%	$255.1715	$255.17	$255.15	$255.20
Purchase #7	$88.64	12.272%	$99.5179	$99.52	$99.50	$99.50
7 purchase totals =	$1,008.88		$1,118.7876	$1,118.79	$1,118.70	$1,118.80