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	$13.98	3.604%	$14.4838	$14.48	$14.50	$14.50
Purchase #2	$64.61	12.142%	$72.4549	$72.45	$72.45	$72.50
Purchase #3	$14.91	5.264%	$15.6949	$15.69	$15.70	$15.70
Purchase #4	$141.54	12.319%	$158.9763	$158.98	$159.00	$159.00
Purchase #5	$11.59	5.535%	$12.2315	$12.23	$12.25	$12.20
Purchase #6	$195.66	12.819%	$220.7417	$220.74	$220.75	$220.70
Purchase #7	$11.75	7.179%	$12.5935	$12.59	$12.60	$12.60
7 purchase totals =	$454.04		$507.1766	$507.16	$507.25	$507.20