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	$122.58	5.140%	$128.8806	$128.88	$128.90	$128.90
Purchase #2	$123.86	6.308%	$131.6731	$131.67	$131.65	$131.70
Purchase #3	$116.84	3.128%	$120.4948	$120.49	$120.50	$120.50
Purchase #4	$57.86	3.438%	$59.8492	$59.85	$59.85	$59.80
Purchase #5	$10.81	8.706%	$11.7511	$11.75	$11.75	$11.80
Purchase #6	$76.71	5.130%	$80.6452	$80.65	$80.65	$80.60
Purchase #7	$200.71	9.161%	$219.097	$219.10	$219.10	$219.10
7 purchase totals =	$709.37		$752.3910	$752.39	$752.40	$752.40