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	$94.29	12.380%	$105.9631	$105.96	$105.95	$106.00
Purchase #2	$154.72	12.422%	$173.9393	$173.94	$173.95	$173.90
Purchase #3	$157.38	8.419%	$170.6298	$170.63	$170.65	$170.60
Purchase #4	$216.82	9.586%	$237.6044	$237.60	$237.60	$237.60
Purchase #5	$70.31	4.715%	$73.6251	$73.63	$73.65	$73.60
Purchase #6	$172.60	10.374%	$190.5055	$190.51	$190.50	$190.50
Purchase #7	$50.94	5.230%	$53.6042	$53.60	$53.60	$53.60
7 purchase totals =	$917.06		$1,005.8714	$1,005.87	$1,005.90	$1,005.80