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	$59.48	5.647%	$62.8388	$62.84	$62.85	$62.80
Purchase #2	$26.54	10.246%	$29.2593	$29.26	$29.25	$29.30
Purchase #3	$65.62	10.500%	$72.5101	$72.51	$72.50	$72.50
Purchase #4	$64.96	8.458%	$70.4543	$70.45	$70.45	$70.50
Purchase #5	$249.95	12.575%	$281.3812	$281.38	$281.40	$281.40
Purchase #6	$45.35	11.108%	$50.3875	$50.39	$50.40	$50.40
Purchase #7	$53.81	7.702%	$57.9544	$57.95	$57.95	$58.00
7 purchase totals =	$565.71		$624.7856	$624.78	$624.80	$624.90