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	$163.54	13.867%	$186.2181	$186.22	$186.20	$186.20
Purchase #2	$20.84	4.781%	$21.8364	$21.84	$21.85	$21.80
Purchase #3	$57.85	8.738%	$62.9049	$62.90	$62.90	$62.90
Purchase #4	$151.46	10.520%	$167.3936	$167.39	$167.40	$167.40
Purchase #5	$57.85	7.436%	$62.1517	$62.15	$62.15	$62.20
Purchase #6	$9.27	5.478%	$9.7778	$9.78	$9.80	$9.80
Purchase #7	$100.86	13.181%	$114.1544	$114.15	$114.15	$114.20
7 purchase totals =	$561.67		$624.4369	$624.43	$624.45	$624.50