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	$149.66	11.266%	$166.5207	$166.52	$166.50	$166.50
Purchase #2	$146.90	10.471%	$162.2819	$162.28	$162.30	$162.30
Purchase #3	$168.38	3.264%	$173.8759	$173.88	$173.90	$173.90
Purchase #4	$94.46	6.725%	$100.8124	$100.81	$100.80	$100.80
Purchase #5	$82.84	4.320%	$86.4187	$86.42	$86.40	$86.40
Purchase #6	$226.75	6.861%	$242.3073	$242.31	$242.30	$242.30
Purchase #7	$30.70	5.651%	$32.4349	$32.43	$32.45	$32.40
7 purchase totals =	$899.69		$964.6518	$964.65	$964.65	$964.60