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	$54.77	12.768%	$61.763	$61.76	$61.75	$61.80
Purchase #2	$27.32	7.860%	$29.4674	$29.47	$29.45	$29.50
Purchase #3	$9.82	8.562%	$10.6608	$10.66	$10.65	$10.70
Purchase #4	$158.82	13.264%	$179.8859	$179.89	$179.90	$179.90
Purchase #5	$155.94	10.725%	$172.6646	$172.66	$172.65	$172.70
Purchase #6	$130.45	11.199%	$145.0591	$145.06	$145.05	$145.10
Purchase #7	$85.55	3.407%	$88.4647	$88.46	$88.45	$88.50
7 purchase totals =	$622.67		$687.9655	$687.96	$687.90	$688.20