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	$98.80	10.457%	$109.1315	$109.13	$109.15	$109.10
Purchase #2	$132.37	11.808%	$148.0002	$148.00	$148.00	$148.00
Purchase #3	$189.44	3.549%	$196.1632	$196.16	$196.15	$196.20
Purchase #4	$26.65	5.206%	$28.0374	$28.04	$28.05	$28.00
Purchase #5	$155.78	7.585%	$167.5959	$167.60	$167.60	$167.60
Purchase #6	$170.94	10.298%	$188.5434	$188.54	$188.55	$188.50
Purchase #7	$86.62	10.578%	$95.7827	$95.78	$95.80	$95.80
7 purchase totals =	$860.60		$933.2543	$933.25	$933.30	$933.20