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	$55.76	9.707%	$61.1726	$61.17	$61.15	$61.20
Purchase #2	$168.72	9.459%	$184.6792	$184.68	$184.70	$184.70
Purchase #3	$208.61	13.356%	$236.472	$236.47	$236.45	$236.50
Purchase #4	$237.25	13.608%	$269.535	$269.54	$269.55	$269.50
Purchase #5	$52.28	3.186%	$53.9456	$53.95	$53.95	$53.90
Purchase #6	$18.60	13.300%	$21.0738	$21.07	$21.05	$21.10
Purchase #7	$203.42	5.698%	$215.0109	$215.01	$215.00	$215.00
7 purchase totals =	$944.64		$1,041.8891	$1,041.89	$1,041.85	$1,041.90