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	$89.27	13.665%	$101.4687	$101.47	$101.45	$101.50
Purchase #2	$30.90	5.551%	$32.6153	$32.62	$32.60	$32.60
Purchase #3	$212.52	6.310%	$225.93	$225.93	$225.95	$225.90
Purchase #4	$45.51	8.516%	$49.3856	$49.39	$49.40	$49.40
Purchase #5	$142.74	3.401%	$147.5946	$147.59	$147.60	$147.60
Purchase #6	$112.45	4.800%	$117.8476	$117.85	$117.85	$117.80
Purchase #7	$17.47	11.800%	$19.5315	$19.53	$19.55	$19.50
7 purchase totals =	$650.86		$694.3733	$694.38	$694.40	$694.30