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	$208.91	4.389%	$218.0791	$218.08	$218.10	$218.10
Purchase #2	$42.78	6.370%	$45.5051	$45.51	$45.50	$45.50
Purchase #3	$126.95	11.413%	$141.4388	$141.44	$141.45	$141.40
Purchase #4	$154.86	6.535%	$164.9801	$164.98	$165.00	$165.00
Purchase #5	$71.35	9.470%	$78.1068	$78.11	$78.10	$78.10
Purchase #6	$153.64	5.817%	$162.5772	$162.58	$162.60	$162.60
Purchase #7	$111.85	6.388%	$118.995	$119.00	$119.00	$119.00
7 purchase totals =	$870.34		$929.6821	$929.70	$929.75	$929.70