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	$84.65	12.788%	$95.475	$95.48	$95.50	$95.50
Purchase #2	$97.65	5.652%	$103.1692	$103.17	$103.15	$103.20
Purchase #3	$131.51	4.526%	$137.4621	$137.46	$137.45	$137.50
Purchase #4	$131.56	13.654%	$149.5232	$149.52	$149.50	$149.50
Purchase #5	$170.88	3.245%	$176.4251	$176.43	$176.45	$176.40
Purchase #6	$61.64	8.747%	$67.0317	$67.03	$67.05	$67.00
Purchase #7	$156.85	13.683%	$178.3118	$178.31	$178.30	$178.30
7 purchase totals =	$834.74		$907.3981	$907.40	$907.40	$907.40