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	$123.63	8.588%	$134.2473	$134.25	$134.25	$134.20
Purchase #2	$6.25	12.457%	$7.0286	$7.03	$7.05	$7.00
Purchase #3	$66.32	3.526%	$68.6584	$68.66	$68.65	$68.70
Purchase #4	$50.72	5.703%	$53.6126	$53.61	$53.60	$53.60
Purchase #5	$45.94	10.541%	$50.7825	$50.78	$50.80	$50.80
Purchase #6	$35.80	4.794%	$37.5163	$37.52	$37.50	$37.50
Purchase #7	$151.77	10.382%	$167.5268	$167.53	$167.55	$167.50
7 purchase totals =	$480.43		$519.3725	$519.38	$519.40	$519.30