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	$156.97	12.178%	$176.0858	$176.09	$176.10	$176.10
Purchase #2	$241.75	11.476%	$269.4932	$269.49	$269.50	$269.50
Purchase #3	$59.78	4.197%	$62.289	$62.29	$62.30	$62.30
Purchase #4	$163.75	9.396%	$179.136	$179.14	$179.15	$179.10
Purchase #5	$126.34	3.872%	$131.2319	$131.23	$131.25	$131.20
Purchase #6	$246.50	9.802%	$270.6619	$270.66	$270.65	$270.70
Purchase #7	$131.72	5.815%	$139.3795	$139.38	$139.40	$139.40
7 purchase totals =	$1,126.81		$1,228.2773	$1,228.28	$1,228.35	$1,228.30