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	$143.30	9.218%	$156.5094	$156.51	$156.50	$156.50
Purchase #2	$116.51	7.599%	$125.3636	$125.36	$125.35	$125.40
Purchase #3	$83.93	7.779%	$90.4589	$90.46	$90.45	$90.50
Purchase #4	$143.60	5.166%	$151.0184	$151.02	$151.00	$151.00
Purchase #5	$99.81	8.808%	$108.6013	$108.60	$108.60	$108.60
Purchase #6	$134.75	9.206%	$147.1551	$147.16	$147.15	$147.20
Purchase #7	$123.39	7.284%	$132.3777	$132.38	$132.40	$132.40
7 purchase totals =	$845.29		$911.4844	$911.49	$911.45	$911.60