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	$64.55	12.653%	$72.7175	$72.72	$72.70	$72.70
Purchase #2	$180.46	5.131%	$189.7194	$189.72	$189.70	$189.70
Purchase #3	$227.96	7.232%	$244.4461	$244.45	$244.45	$244.40
Purchase #4	$20.37	10.572%	$22.5235	$22.52	$22.50	$22.50
Purchase #5	$52.71	7.624%	$56.7286	$56.73	$56.75	$56.70
Purchase #6	$156.96	13.669%	$178.4149	$178.41	$178.40	$178.40
Purchase #7	$53.98	13.525%	$61.2808	$61.28	$61.30	$61.30
7 purchase totals =	$756.99		$825.8308	$825.83	$825.80	$825.70