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	$138.51	8.413%	$150.1628	$150.16	$150.15	$150.20
Purchase #2	$234.87	8.769%	$255.4658	$255.47	$255.45	$255.50
Purchase #3	$144.56	6.158%	$153.462	$153.46	$153.45	$153.50
Purchase #4	$233.77	8.831%	$254.4142	$254.41	$254.40	$254.40
Purchase #5	$44.50	4.548%	$46.5239	$46.52	$46.50	$46.50
Purchase #6	$55.69	6.658%	$59.3978	$59.40	$59.40	$59.40
Purchase #7	$175.26	11.351%	$195.1538	$195.15	$195.15	$195.20
7 purchase totals =	$1,027.16		$1,114.5803	$1,114.57	$1,114.50	$1,114.70