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	$208.58	5.114%	$219.2468	$219.25	$219.25	$219.20
Purchase #2	$167.69	6.810%	$179.1097	$179.11	$179.10	$179.10
Purchase #3	$194.94	13.786%	$221.8144	$221.81	$221.80	$221.80
Purchase #4	$164.30	12.497%	$184.8326	$184.83	$184.85	$184.80
Purchase #5	$240.53	10.395%	$265.5331	$265.53	$265.55	$265.50
Purchase #6	$74.27	12.495%	$83.55	$83.55	$83.55	$83.60
Purchase #7	$248.47	10.632%	$274.8873	$274.89	$274.90	$274.90
7 purchase totals =	$1,298.78		$1,428.9739	$1,428.97	$1,429.00	$1,428.90