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	$214.80	7.121%	$230.0959	$230.10	$230.10	$230.10
Purchase #2	$88.52	13.502%	$100.472	$100.47	$100.45	$100.50
Purchase #3	$35.97	4.758%	$37.6815	$37.68	$37.70	$37.70
Purchase #4	$104.39	3.397%	$107.9361	$107.94	$107.95	$107.90
Purchase #5	$26.33	4.129%	$27.4172	$27.42	$27.40	$27.40
Purchase #6	$194.61	12.280%	$218.5081	$218.51	$218.50	$218.50
Purchase #7	$19.61	4.508%	$20.494	$20.49	$20.50	$20.50
7 purchase totals =	$684.23		$742.6048	$742.61	$742.60	$742.60