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	$26.77	10.766%	$29.6521	$29.65	$29.65	$29.70
Purchase #2	$20.34	12.105%	$22.8022	$22.80	$22.80	$22.80
Purchase #3	$156.90	4.783%	$164.4045	$164.40	$164.40	$164.40
Purchase #4	$79.33	6.521%	$84.5031	$84.50	$84.50	$84.50
Purchase #5	$236.54	11.555%	$263.8722	$263.87	$263.85	$263.90
Purchase #6	$107.83	3.231%	$111.314	$111.31	$111.30	$111.30
Purchase #7	$145.60	10.806%	$161.3335	$161.33	$161.35	$161.30
7 purchase totals =	$773.31		$837.8816	$837.86	$837.85	$837.90