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	$187.51	9.649%	$205.6028	$205.60	$205.60	$205.60
Purchase #2	$62.46	8.747%	$67.9234	$67.92	$67.90	$67.90
Purchase #3	$228.85	9.476%	$250.5358	$250.54	$250.55	$250.50
Purchase #4	$46.80	4.541%	$48.9252	$48.93	$48.95	$48.90
Purchase #5	$29.95	5.492%	$31.5949	$31.59	$31.60	$31.60
Purchase #6	$94.79	12.441%	$106.5828	$106.58	$106.60	$106.60
Purchase #7	$168.70	13.379%	$191.2704	$191.27	$191.25	$191.30
7 purchase totals =	$819.06		$902.4353	$902.43	$902.45	$902.40