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	$235.91	8.156%	$255.1508	$255.15	$255.15	$255.20
Purchase #2	$188.80	9.515%	$206.7643	$206.76	$206.75	$206.80
Purchase #3	$85.37	3.504%	$88.3614	$88.36	$88.35	$88.40
Purchase #4	$150.91	12.361%	$169.564	$169.56	$169.55	$169.60
Purchase #5	$23.30	6.141%	$24.7309	$24.73	$24.75	$24.70
Purchase #6	$151.59	4.725%	$158.7526	$158.75	$158.75	$158.80
Purchase #7	$107.73	5.445%	$113.5959	$113.60	$113.60	$113.60
7 purchase totals =	$943.61		$1,016.9199	$1,016.91	$1,016.90	$1,017.10