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	$113.71	4.186%	$118.4699	$118.47	$118.45	$118.50
Purchase #2	$132.63	11.790%	$148.2671	$148.27	$148.25	$148.30
Purchase #3	$70.86	9.442%	$77.5506	$77.55	$77.55	$77.60
Purchase #4	$148.77	5.178%	$156.4733	$156.47	$156.45	$156.50
Purchase #5	$102.34	5.792%	$108.2675	$108.27	$108.25	$108.30
Purchase #6	$17.83	3.217%	$18.4036	$18.40	$18.40	$18.40
Purchase #7	$64.51	5.110%	$67.8065	$67.81	$67.80	$67.80
7 purchase totals =	$650.65		$695.2385	$695.24	$695.15	$695.40