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	$62.42	8.479%	$67.7126	$67.71	$67.70	$67.70
Purchase #2	$77.55	5.429%	$81.7602	$81.76	$81.75	$81.80
Purchase #3	$58.55	6.329%	$62.2556	$62.26	$62.25	$62.30
Purchase #4	$146.93	10.486%	$162.3371	$162.34	$162.35	$162.30
Purchase #5	$129.55	9.204%	$141.4738	$141.47	$141.45	$141.50
Purchase #6	$104.77	6.303%	$111.3737	$111.37	$111.35	$111.40
Purchase #7	$225.30	3.576%	$233.3567	$233.36	$233.35	$233.40
7 purchase totals =	$805.07		$860.2697	$860.27	$860.20	$860.40