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	$35.71	5.636%	$37.7226	$37.72	$37.70	$37.70
Purchase #2	$182.52	7.853%	$196.8533	$196.85	$196.85	$196.90
Purchase #3	$22.28	8.320%	$24.1337	$24.13	$24.15	$24.10
Purchase #4	$70.87	3.702%	$73.4936	$73.49	$73.50	$73.50
Purchase #5	$19.32	5.771%	$20.435	$20.44	$20.45	$20.40
Purchase #6	$38.69	3.476%	$40.0349	$40.03	$40.05	$40.00
Purchase #7	$173.59	6.210%	$184.3699	$184.37	$184.35	$184.40
7 purchase totals =	$542.98		$577.0430	$577.03	$577.05	$577.00