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	$132.52	12.265%	$148.7736	$148.77	$148.75	$148.80
Purchase #2	$85.58	4.600%	$89.5167	$89.52	$89.50	$89.50
Purchase #3	$82.60	6.142%	$87.6733	$87.67	$87.65	$87.70
Purchase #4	$199.64	6.856%	$213.3273	$213.33	$213.35	$213.30
Purchase #5	$148.58	9.571%	$162.8006	$162.80	$162.80	$162.80
Purchase #6	$237.33	7.535%	$255.2128	$255.21	$255.20	$255.20
Purchase #7	$232.73	11.139%	$258.6538	$258.65	$258.65	$258.70
7 purchase totals =	$1,118.98		$1,215.9581	$1,215.95	$1,215.90	$1,216.00