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	$109.52	3.730%	$113.6051	$113.61	$113.60	$113.60
Purchase #2	$90.27	6.650%	$96.273	$96.27	$96.25	$96.30
Purchase #3	$30.41	12.751%	$34.2876	$34.29	$34.30	$34.30
Purchase #4	$171.27	5.189%	$180.1572	$180.16	$180.15	$180.20
Purchase #5	$166.32	4.361%	$173.5732	$173.57	$173.55	$173.60
Purchase #6	$199.53	9.120%	$217.7271	$217.73	$217.75	$217.70
Purchase #7	$102.43	8.777%	$111.4203	$111.42	$111.40	$111.40
7 purchase totals =	$869.75		$927.0435	$927.05	$927.00	$927.10