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	$162.31	13.554%	$184.3095	$184.31	$184.30	$184.30
Purchase #2	$86.80	11.622%	$96.8879	$96.89	$96.90	$96.90
Purchase #3	$53.74	11.149%	$59.7315	$59.73	$59.75	$59.70
Purchase #4	$36.32	3.371%	$37.5443	$37.54	$37.55	$37.50
Purchase #5	$144.55	13.269%	$163.7303	$163.73	$163.75	$163.70
Purchase #6	$87.38	3.672%	$90.5886	$90.59	$90.60	$90.60
Purchase #7	$121.37	7.857%	$130.906	$130.91	$130.90	$130.90
7 purchase totals =	$692.47		$763.6981	$763.70	$763.75	$763.60