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	$53.82	11.420%	$59.9662	$59.97	$59.95	$60.00
Purchase #2	$136.65	10.388%	$150.8452	$150.85	$150.85	$150.80
Purchase #3	$12.86	7.396%	$13.8111	$13.81	$13.80	$13.80
Purchase #4	$216.70	3.311%	$223.8749	$223.87	$223.85	$223.90
Purchase #5	$60.82	5.528%	$64.1821	$64.18	$64.20	$64.20
Purchase #6	$121.36	5.104%	$127.5542	$127.55	$127.55	$127.60
Purchase #7	$72.39	12.144%	$81.181	$81.18	$81.20	$81.20
7 purchase totals =	$674.60		$721.4147	$721.41	$721.40	$721.50