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	$63.61	6.253%	$67.5875	$67.59	$67.60	$67.60
Purchase #2	$52.71	13.591%	$59.8738	$59.87	$59.85	$59.90
Purchase #3	$19.31	4.345%	$20.149	$20.15	$20.15	$20.10
Purchase #4	$153.26	6.693%	$163.5177	$163.52	$163.50	$163.50
Purchase #5	$83.27	11.195%	$92.5921	$92.59	$92.60	$92.60
Purchase #6	$55.63	3.135%	$57.374	$57.37	$57.35	$57.40
Purchase #7	$46.28	12.227%	$51.9387	$51.94	$51.95	$51.90
7 purchase totals =	$474.07		$513.0328	$513.03	$513.00	$513.00