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	$53.82	13.458%	$61.0631	$61.06	$61.05	$61.10
Purchase #2	$243.59	9.427%	$266.5532	$266.55	$266.55	$266.60
Purchase #3	$25.69	8.396%	$27.8469	$27.85	$27.85	$27.80
Purchase #4	$116.93	7.615%	$125.8342	$125.83	$125.85	$125.80
Purchase #5	$77.27	10.126%	$85.0944	$85.09	$85.10	$85.10
Purchase #6	$54.75	10.278%	$60.3772	$60.38	$60.40	$60.40
Purchase #7	$79.86	7.773%	$86.0675	$86.07	$86.05	$86.10
7 purchase totals =	$651.91		$712.8365	$712.83	$712.85	$712.90