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	$52.61	3.196%	$54.2914	$54.29	$54.30	$54.30
Purchase #2	$148.58	4.566%	$155.3642	$155.36	$155.35	$155.40
Purchase #3	$238.78	13.649%	$271.3711	$271.37	$271.35	$271.40
Purchase #4	$190.82	9.497%	$208.9422	$208.94	$208.95	$208.90
Purchase #5	$202.90	12.268%	$227.7918	$227.79	$227.80	$227.80
Purchase #6	$81.52	13.110%	$92.2073	$92.21	$92.20	$92.20
Purchase #7	$73.51	5.379%	$77.4641	$77.46	$77.45	$77.50
7 purchase totals =	$988.72		$1,087.4321	$1,087.42	$1,087.40	$1,087.50