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	$140.71	4.735%	$147.3726	$147.37	$147.35	$147.40
Purchase #2	$114.79	8.528%	$124.5793	$124.58	$124.60	$124.60
Purchase #3	$146.25	3.339%	$151.1333	$151.13	$151.15	$151.10
Purchase #4	$200.32	8.438%	$217.223	$217.22	$217.20	$217.20
Purchase #5	$205.37	13.172%	$232.4213	$232.42	$232.40	$232.40
Purchase #6	$93.42	11.479%	$104.1437	$104.14	$104.15	$104.10
Purchase #7	$81.87	10.595%	$90.5441	$90.54	$90.55	$90.50
7 purchase totals =	$982.73		$1,067.4173	$1,067.40	$1,067.40	$1,067.30