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	$138.73	8.451%	$150.4541	$150.45	$150.45	$150.50
Purchase #2	$114.55	10.297%	$126.3452	$126.35	$126.35	$126.30
Purchase #3	$137.28	3.594%	$142.2138	$142.21	$142.20	$142.20
Purchase #4	$115.74	13.612%	$131.4945	$131.49	$131.50	$131.50
Purchase #5	$214.50	5.515%	$226.3297	$226.33	$226.35	$226.30
Purchase #6	$85.34	11.464%	$95.1234	$95.12	$95.10	$95.10
Purchase #7	$127.88	13.210%	$144.7729	$144.77	$144.75	$144.80
7 purchase totals =	$934.02		$1,016.7336	$1,016.72	$1,016.70	$1,016.70