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	$208.32	6.709%	$222.2962	$222.30	$222.30	$222.30
Purchase #2	$203.29	5.577%	$214.6275	$214.63	$214.65	$214.60
Purchase #3	$241.85	6.861%	$258.4433	$258.44	$258.45	$258.40
Purchase #4	$106.95	4.436%	$111.6943	$111.69	$111.70	$111.70
Purchase #5	$75.31	9.338%	$82.3424	$82.34	$82.35	$82.30
Purchase #6	$35.51	7.311%	$38.1061	$38.11	$38.10	$38.10
Purchase #7	$67.34	8.330%	$72.9494	$72.95	$72.95	$72.90
7 purchase totals =	$938.57		$1,000.4592	$1,000.46	$1,000.50	$1,000.30