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	$54.65	13.291%	$61.9135	$61.91	$61.90	$61.90
Purchase #2	$63.30	4.857%	$66.3745	$66.37	$66.35	$66.40
Purchase #3	$69.67	10.594%	$77.0508	$77.05	$77.05	$77.10
Purchase #4	$214.28	3.290%	$221.3298	$221.33	$221.35	$221.30
Purchase #5	$101.40	11.307%	$112.8653	$112.87	$112.85	$112.90
Purchase #6	$59.71	9.638%	$65.4648	$65.46	$65.45	$65.50
Purchase #7	$205.30	7.361%	$220.4121	$220.41	$220.40	$220.40
7 purchase totals =	$768.31		$825.4108	$825.40	$825.35	$825.50