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	$241.86	5.187%	$254.4053	$254.41	$254.40	$254.40
Purchase #2	$20.50	5.240%	$21.5742	$21.57	$21.55	$21.60
Purchase #3	$193.52	9.746%	$212.3805	$212.38	$212.40	$212.40
Purchase #4	$151.51	12.766%	$170.8518	$170.85	$170.85	$170.90
Purchase #5	$76.26	3.168%	$78.6759	$78.68	$78.70	$78.70
Purchase #6	$190.82	12.325%	$214.3386	$214.34	$214.35	$214.30
Purchase #7	$81.92	8.244%	$88.6735	$88.67	$88.65	$88.70
7 purchase totals =	$956.39		$1,040.8998	$1,040.90	$1,040.90	$1,041.00