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	$199.31	4.503%	$208.2849	$208.28	$208.30	$208.30
Purchase #2	$36.80	13.241%	$41.6727	$41.67	$41.65	$41.70
Purchase #3	$139.33	8.172%	$150.716	$150.72	$150.70	$150.70
Purchase #4	$53.50	10.341%	$59.0324	$59.03	$59.05	$59.00
Purchase #5	$153.86	13.224%	$174.2064	$174.21	$174.20	$174.20
Purchase #6	$122.58	10.633%	$135.6139	$135.61	$135.60	$135.60
Purchase #7	$98.82	12.777%	$111.4462	$111.45	$111.45	$111.40
7 purchase totals =	$804.20		$880.9725	$880.97	$880.95	$880.90