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	$174.34	3.318%	$180.1246	$180.12	$180.10	$180.10
Purchase #2	$190.81	12.396%	$214.4628	$214.46	$214.45	$214.50
Purchase #3	$154.44	8.749%	$167.952	$167.95	$167.95	$168.00
Purchase #4	$17.78	12.710%	$20.0398	$20.04	$20.05	$20.00
Purchase #5	$105.37	5.720%	$111.3972	$111.40	$111.40	$111.40
Purchase #6	$149.47	5.874%	$158.2499	$158.25	$158.25	$158.20
Purchase #7	$211.34	10.451%	$233.4271	$233.43	$233.45	$233.40
7 purchase totals =	$1,003.55		$1,085.6534	$1,085.65	$1,085.65	$1,085.60