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	$95.82	4.352%	$99.9901	$99.99	$100.00	$100.00
Purchase #2	$54.56	12.264%	$61.2512	$61.25	$61.25	$61.30
Purchase #3	$171.30	4.554%	$179.101	$179.10	$179.10	$179.10
Purchase #4	$125.83	9.152%	$137.346	$137.35	$137.35	$137.30
Purchase #5	$126.60	8.551%	$137.4256	$137.43	$137.45	$137.40
Purchase #6	$186.69	7.481%	$200.6563	$200.66	$200.65	$200.70
Purchase #7	$102.92	11.394%	$114.6467	$114.65	$114.65	$114.60
7 purchase totals =	$863.72		$930.4169	$930.43	$930.45	$930.40