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	$249.83	5.630%	$263.8954	$263.90	$263.90	$263.90
Purchase #2	$91.52	11.729%	$102.2544	$102.25	$102.25	$102.30
Purchase #3	$187.49	12.182%	$210.33	$210.33	$210.35	$210.30
Purchase #4	$14.43	3.778%	$14.9752	$14.98	$15.00	$15.00
Purchase #5	$63.59	13.377%	$72.0964	$72.10	$72.10	$72.10
Purchase #6	$116.64	13.666%	$132.58	$132.58	$132.60	$132.60
Purchase #7	$106.83	6.138%	$113.3872	$113.39	$113.40	$113.40
7 purchase totals =	$830.33		$909.5186	$909.53	$909.60	$909.60