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	$34.64	7.842%	$37.3565	$37.36	$37.35	$37.40
Purchase #2	$77.29	8.298%	$83.7035	$83.70	$83.70	$83.70
Purchase #3	$43.62	3.536%	$45.1624	$45.16	$45.15	$45.20
Purchase #4	$178.57	5.760%	$188.8556	$188.86	$188.85	$188.90
Purchase #5	$87.65	13.670%	$99.6318	$99.63	$99.65	$99.60
Purchase #6	$222.82	13.248%	$252.3392	$252.34	$252.35	$252.30
Purchase #7	$53.27	5.172%	$56.0251	$56.03	$56.05	$56.00
7 purchase totals =	$697.86		$763.0741	$763.08	$763.10	$763.10