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	$243.41	12.793%	$274.5494	$274.55	$274.55	$274.50
Purchase #2	$12.52	10.743%	$13.865	$13.87	$13.85	$13.90
Purchase #3	$13.94	11.462%	$15.5378	$15.54	$15.55	$15.50
Purchase #4	$122.84	3.815%	$127.5263	$127.53	$127.55	$127.50
Purchase #5	$18.52	10.178%	$20.405	$20.41	$20.40	$20.40
Purchase #6	$212.73	7.564%	$228.8209	$228.82	$228.80	$228.80
Purchase #7	$203.28	13.847%	$231.4282	$231.43	$231.45	$231.40
7 purchase totals =	$827.24		$912.1326	$912.15	$912.15	$912.00