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	$64.81	11.455%	$72.234	$72.23	$72.25	$72.20
Purchase #2	$17.42	7.154%	$18.6662	$18.67	$18.65	$18.70
Purchase #3	$86.61	3.832%	$89.9289	$89.93	$89.95	$89.90
Purchase #4	$82.44	9.250%	$90.0657	$90.07	$90.05	$90.10
Purchase #5	$58.70	9.859%	$64.4872	$64.49	$64.50	$64.50
Purchase #6	$164.85	8.582%	$178.9974	$179.00	$179.00	$179.00
Purchase #7	$184.34	11.392%	$205.34	$205.34	$205.35	$205.30
7 purchase totals =	$659.17		$719.7194	$719.73	$719.75	$719.70