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	$175.90	11.696%	$196.4733	$196.47	$196.45	$196.50
Purchase #2	$44.56	6.808%	$47.5936	$47.59	$47.60	$47.60
Purchase #3	$38.90	13.718%	$44.2363	$44.24	$44.25	$44.20
Purchase #4	$48.64	12.369%	$54.6563	$54.66	$54.65	$54.70
Purchase #5	$180.70	12.365%	$203.0436	$203.04	$203.05	$203.00
Purchase #6	$34.67	13.847%	$39.4708	$39.47	$39.45	$39.50
Purchase #7	$135.88	4.244%	$141.6467	$141.65	$141.65	$141.60
7 purchase totals =	$659.25		$727.1206	$727.12	$727.10	$727.10