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	$236.44	4.307%	$246.6235	$246.62	$246.60	$246.60
Purchase #2	$29.37	6.482%	$31.2738	$31.27	$31.25	$31.30
Purchase #3	$142.47	8.453%	$154.513	$154.51	$154.50	$154.50
Purchase #4	$229.34	8.402%	$248.6091	$248.61	$248.60	$248.60
Purchase #5	$124.74	6.613%	$132.9891	$132.99	$133.00	$133.00
Purchase #6	$102.42	7.245%	$109.8403	$109.84	$109.85	$109.80
Purchase #7	$133.45	3.362%	$137.9366	$137.94	$137.95	$137.90
7 purchase totals =	$998.23		$1,061.7854	$1,061.78	$1,061.75	$1,061.70