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	$116.38	11.418%	$129.6683	$129.67	$129.65	$129.70
Purchase #2	$99.31	6.162%	$105.4295	$105.43	$105.45	$105.40
Purchase #3	$43.55	5.527%	$45.957	$45.96	$45.95	$46.00
Purchase #4	$59.30	10.499%	$65.5259	$65.53	$65.55	$65.50
Purchase #5	$24.79	11.468%	$27.6329	$27.63	$27.65	$27.60
Purchase #6	$248.25	4.141%	$258.53	$258.53	$258.55	$258.50
Purchase #7	$17.78	4.779%	$18.6297	$18.63	$18.65	$18.60
7 purchase totals =	$609.36		$651.3733	$651.38	$651.45	$651.30