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	$13.78	6.232%	$14.6388	$14.64	$14.65	$14.60
Purchase #2	$68.54	10.739%	$75.9005	$75.90	$75.90	$75.90
Purchase #3	$10.27	10.510%	$11.3494	$11.35	$11.35	$11.30
Purchase #4	$80.39	6.471%	$85.592	$85.59	$85.60	$85.60
Purchase #5	$77.91	4.585%	$81.4822	$81.48	$81.50	$81.50
Purchase #6	$244.31	7.400%	$262.3889	$262.39	$262.40	$262.40
Purchase #7	$55.62	6.543%	$59.2592	$59.26	$59.25	$59.30
7 purchase totals =	$550.82		$590.6110	$590.61	$590.65	$590.60