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	$200.43	9.197%	$218.8635	$218.86	$218.85	$218.90
Purchase #2	$9.56	10.573%	$10.5708	$10.57	$10.55	$10.60
Purchase #3	$48.78	12.712%	$54.9809	$54.98	$55.00	$55.00
Purchase #4	$36.26	3.577%	$37.557	$37.56	$37.55	$37.60
Purchase #5	$69.87	11.599%	$77.9742	$77.97	$77.95	$78.00
Purchase #6	$149.64	8.606%	$162.518	$162.52	$162.50	$162.50
Purchase #7	$65.68	11.691%	$73.3586	$73.36	$73.35	$73.40
7 purchase totals =	$580.22		$635.8230	$635.82	$635.75	$636.00