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	$88.44	4.633%	$92.5374	$92.54	$92.55	$92.50
Purchase #2	$170.72	5.702%	$180.4545	$180.45	$180.45	$180.50
Purchase #3	$37.90	3.515%	$39.2322	$39.23	$39.25	$39.20
Purchase #4	$146.68	3.294%	$151.5116	$151.51	$151.50	$151.50
Purchase #5	$51.66	5.386%	$54.4424	$54.44	$54.45	$54.40
Purchase #6	$20.42	5.795%	$21.6033	$21.60	$21.60	$21.60
Purchase #7	$211.79	12.497%	$238.2574	$238.26	$238.25	$238.30
7 purchase totals =	$727.61		$778.0388	$778.03	$778.05	$778.00