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	$146.72	10.318%	$161.8586	$161.86	$161.85	$161.90
Purchase #2	$200.37	9.388%	$219.1807	$219.18	$219.20	$219.20
Purchase #3	$138.60	12.712%	$156.2188	$156.22	$156.20	$156.20
Purchase #4	$175.41	4.157%	$182.7018	$182.70	$182.70	$182.70
Purchase #5	$63.61	13.554%	$72.2317	$72.23	$72.25	$72.20
Purchase #6	$111.94	5.821%	$118.456	$118.46	$118.45	$118.50
Purchase #7	$77.77	11.791%	$86.9399	$86.94	$86.95	$86.90
7 purchase totals =	$914.42		$997.5875	$997.59	$997.60	$997.60