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	$132.81	8.164%	$143.6526	$143.65	$143.65	$143.70
Purchase #2	$164.98	13.575%	$187.376	$187.38	$187.40	$187.40
Purchase #3	$166.86	3.650%	$172.9504	$172.95	$172.95	$173.00
Purchase #4	$123.80	8.788%	$134.6795	$134.68	$134.70	$134.70
Purchase #5	$49.71	11.262%	$55.3083	$55.31	$55.30	$55.30
Purchase #6	$187.96	12.818%	$212.0527	$212.05	$212.05	$212.10
Purchase #7	$99.55	13.786%	$113.274	$113.27	$113.25	$113.30
7 purchase totals =	$925.67		$1,019.2935	$1,019.29	$1,019.30	$1,019.50