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	$59.92	10.525%	$66.2266	$66.23	$66.25	$66.20
Purchase #2	$187.29	7.144%	$200.67	$200.67	$200.65	$200.70
Purchase #3	$104.71	7.406%	$112.4648	$112.46	$112.45	$112.50
Purchase #4	$50.54	6.727%	$53.9398	$53.94	$53.95	$53.90
Purchase #5	$212.60	6.848%	$227.1588	$227.16	$227.15	$227.20
Purchase #6	$206.43	4.800%	$216.3386	$216.34	$216.35	$216.30
Purchase #7	$40.48	7.764%	$43.6229	$43.62	$43.60	$43.60
7 purchase totals =	$861.97		$920.4215	$920.42	$920.40	$920.40