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	$82.42	5.483%	$86.9391	$86.94	$86.95	$86.90
Purchase #2	$78.51	9.725%	$86.1451	$86.15	$86.15	$86.10
Purchase #3	$238.67	6.107%	$253.2456	$253.25	$253.25	$253.20
Purchase #4	$119.57	7.450%	$128.478	$128.48	$128.50	$128.50
Purchase #5	$94.49	4.360%	$98.6098	$98.61	$98.60	$98.60
Purchase #6	$62.61	3.794%	$64.9854	$64.99	$65.00	$65.00
Purchase #7	$237.69	8.795%	$258.5948	$258.59	$258.60	$258.60
7 purchase totals =	$913.96		$976.9978	$977.01	$977.05	$976.90