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	$177.51	10.573%	$196.2781	$196.28	$196.30	$196.30
Purchase #2	$228.32	6.135%	$242.3274	$242.33	$242.35	$242.30
Purchase #3	$44.51	9.596%	$48.7812	$48.78	$48.80	$48.80
Purchase #4	$27.92	5.660%	$29.5003	$29.50	$29.50	$29.50
Purchase #5	$91.33	8.701%	$99.2766	$99.28	$99.30	$99.30
Purchase #6	$131.73	11.775%	$147.2412	$147.24	$147.25	$147.20
Purchase #7	$139.45	11.504%	$155.4923	$155.49	$155.50	$155.50
7 purchase totals =	$840.77		$918.8971	$918.90	$919.00	$918.90