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	$152.51	13.855%	$173.6403	$173.64	$173.65	$173.60
Purchase #2	$133.54	4.437%	$139.4652	$139.47	$139.45	$139.50
Purchase #3	$200.41	12.541%	$225.5434	$225.54	$225.55	$225.50
Purchase #4	$144.52	13.653%	$164.2513	$164.25	$164.25	$164.30
Purchase #5	$215.93	11.426%	$240.6022	$240.60	$240.60	$240.60
Purchase #6	$112.95	8.622%	$122.6885	$122.69	$122.70	$122.70
Purchase #7	$137.62	4.253%	$143.473	$143.47	$143.45	$143.50
7 purchase totals =	$1,097.48		$1,209.6639	$1,209.66	$1,209.65	$1,209.70