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	$128.47	4.613%	$134.3963	$134.40	$134.40	$134.40
Purchase #2	$17.35	9.408%	$18.9823	$18.98	$19.00	$19.00
Purchase #3	$232.61	11.549%	$259.4741	$259.47	$259.45	$259.50
Purchase #4	$192.90	11.170%	$214.4469	$214.45	$214.45	$214.40
Purchase #5	$184.65	6.652%	$196.9329	$196.93	$196.95	$196.90
Purchase #6	$47.51	13.361%	$53.8578	$53.86	$53.85	$53.90
Purchase #7	$139.55	3.857%	$144.9324	$144.93	$144.95	$144.90
7 purchase totals =	$943.04		$1,023.0227	$1,023.02	$1,023.05	$1,023.00