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	$54.98	9.540%	$60.2251	$60.23	$60.25	$60.20
Purchase #2	$13.56	9.773%	$14.8852	$14.89	$14.90	$14.90
Purchase #3	$39.89	5.439%	$42.0596	$42.06	$42.05	$42.10
Purchase #4	$169.30	4.849%	$177.5094	$177.51	$177.50	$177.50
Purchase #5	$119.70	9.676%	$131.2822	$131.28	$131.30	$131.30
Purchase #6	$33.44	4.578%	$34.9709	$34.97	$34.95	$35.00
Purchase #7	$145.60	6.769%	$155.4557	$155.46	$155.45	$155.50
7 purchase totals =	$576.47		$616.3881	$616.40	$616.40	$616.50