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	$142.55	5.516%	$150.4131	$150.41	$150.40	$150.40
Purchase #2	$204.25	12.846%	$230.488	$230.49	$230.50	$230.50
Purchase #3	$216.63	9.829%	$237.9226	$237.92	$237.90	$237.90
Purchase #4	$104.51	11.390%	$116.4137	$116.41	$116.40	$116.40
Purchase #5	$46.62	12.807%	$52.5906	$52.59	$52.60	$52.60
Purchase #6	$100.40	3.557%	$103.9712	$103.97	$103.95	$104.00
Purchase #7	$145.97	12.446%	$164.1374	$164.14	$164.15	$164.10
7 purchase totals =	$960.93		$1,055.9366	$1,055.93	$1,055.90	$1,055.90