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	$177.61	3.649%	$184.091	$184.09	$184.10	$184.10
Purchase #2	$85.29	4.840%	$89.418	$89.42	$89.40	$89.40
Purchase #3	$164.57	12.114%	$184.506	$184.51	$184.50	$184.50
Purchase #4	$178.38	13.725%	$202.8627	$202.86	$202.85	$202.90
Purchase #5	$46.34	13.215%	$52.4638	$52.46	$52.45	$52.50
Purchase #6	$34.50	11.272%	$38.3888	$38.39	$38.40	$38.40
Purchase #7	$223.58	9.311%	$244.3975	$244.40	$244.40	$244.40
7 purchase totals =	$910.27		$996.1278	$996.13	$996.10	$996.20