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	$87.71	9.202%	$95.7811	$95.78	$95.80	$95.80
Purchase #2	$172.48	7.803%	$185.9386	$185.94	$185.95	$185.90
Purchase #3	$228.72	12.112%	$256.4226	$256.42	$256.40	$256.40
Purchase #4	$19.79	7.750%	$21.3237	$21.32	$21.30	$21.30
Purchase #5	$138.57	10.423%	$153.0132	$153.01	$153.00	$153.00
Purchase #6	$47.92	6.763%	$51.1608	$51.16	$51.15	$51.20
Purchase #7	$129.31	12.525%	$145.5061	$145.51	$145.50	$145.50
7 purchase totals =	$824.50		$909.1461	$909.14	$909.10	$909.10