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	$88.76	13.470%	$100.716	$100.72	$100.70	$100.70
Purchase #2	$100.71	4.229%	$104.969	$104.97	$104.95	$105.00
Purchase #3	$25.42	8.743%	$27.6425	$27.64	$27.65	$27.60
Purchase #4	$6.42	7.838%	$6.9232	$6.92	$6.90	$6.90
Purchase #5	$156.50	10.348%	$172.6946	$172.69	$172.70	$172.70
Purchase #6	$172.85	6.695%	$184.4223	$184.42	$184.40	$184.40
Purchase #7	$19.95	10.106%	$21.9661	$21.97	$21.95	$22.00
7 purchase totals =	$570.61		$619.3337	$619.33	$619.25	$619.30