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	$74.95	10.510%	$82.8272	$82.83	$82.85	$82.80
Purchase #2	$237.38	7.591%	$255.3995	$255.40	$255.40	$255.40
Purchase #3	$58.86	6.590%	$62.7389	$62.74	$62.75	$62.70
Purchase #4	$124.35	5.580%	$131.2887	$131.29	$131.30	$131.30
Purchase #5	$119.96	10.236%	$132.2391	$132.24	$132.25	$132.20
Purchase #6	$14.36	3.474%	$14.8589	$14.86	$14.85	$14.90
Purchase #7	$32.52	13.240%	$36.8256	$36.83	$36.85	$36.80
7 purchase totals =	$662.38		$716.1779	$716.19	$716.25	$716.10