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	$14.28	5.590%	$15.0783	$15.08	$15.10	$15.10
Purchase #2	$174.75	7.841%	$188.4521	$188.45	$188.45	$188.50
Purchase #3	$19.30	11.168%	$21.4554	$21.46	$21.45	$21.50
Purchase #4	$109.33	11.228%	$121.6056	$121.61	$121.60	$121.60
Purchase #5	$76.40	6.422%	$81.3064	$81.31	$81.30	$81.30
Purchase #6	$155.87	4.265%	$162.5179	$162.52	$162.50	$162.50
Purchase #7	$127.73	5.320%	$134.5252	$134.53	$134.55	$134.50
7 purchase totals =	$677.66		$724.9409	$724.96	$724.95	$725.00