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	$34.85	6.773%	$37.2104	$37.21	$37.20	$37.20
Purchase #2	$170.70	8.396%	$185.032	$185.03	$185.05	$185.00
Purchase #3	$165.45	12.575%	$186.2553	$186.26	$186.25	$186.30
Purchase #4	$175.52	13.652%	$199.482	$199.48	$199.50	$199.50
Purchase #5	$112.51	5.388%	$118.572	$118.57	$118.55	$118.60
Purchase #6	$52.71	3.762%	$54.693	$54.69	$54.70	$54.70
Purchase #7	$244.61	7.364%	$262.6231	$262.62	$262.60	$262.60
7 purchase totals =	$956.35		$1,043.8678	$1,043.86	$1,043.85	$1,043.90