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	$162.71	4.224%	$169.5829	$169.58	$169.60	$169.60
Purchase #2	$74.76	10.239%	$82.4147	$82.41	$82.40	$82.40
Purchase #3	$153.61	7.199%	$164.6684	$164.67	$164.65	$164.70
Purchase #4	$136.86	13.425%	$155.2335	$155.23	$155.25	$155.20
Purchase #5	$207.44	12.604%	$233.5857	$233.59	$233.60	$233.60
Purchase #6	$176.69	3.759%	$183.3318	$183.33	$183.35	$183.30
Purchase #7	$145.43	5.102%	$152.8498	$152.85	$152.85	$152.80
7 purchase totals =	$1,057.50		$1,141.6668	$1,141.66	$1,141.70	$1,141.60