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	$145.88	10.698%	$161.4862	$161.49	$161.50	$161.50
Purchase #2	$187.67	6.347%	$199.5814	$199.58	$199.60	$199.60
Purchase #3	$9.71	9.116%	$10.5952	$10.60	$10.60	$10.60
Purchase #4	$219.64	10.482%	$242.6627	$242.66	$242.65	$242.70
Purchase #5	$84.94	6.703%	$90.6335	$90.63	$90.65	$90.60
Purchase #6	$229.96	13.356%	$260.6735	$260.67	$260.65	$260.70
Purchase #7	$178.37	10.126%	$196.4317	$196.43	$196.45	$196.40
7 purchase totals =	$1,056.17		$1,162.0642	$1,162.06	$1,162.10	$1,162.10