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	$178.26	10.353%	$196.7153	$196.72	$196.70	$196.70
Purchase #2	$19.35	9.477%	$21.1838	$21.18	$21.20	$21.20
Purchase #3	$14.35	6.210%	$15.2411	$15.24	$15.25	$15.20
Purchase #4	$182.88	4.341%	$190.8188	$190.82	$190.80	$190.80
Purchase #5	$126.25	9.645%	$138.4268	$138.43	$138.45	$138.40
Purchase #6	$58.29	7.769%	$62.8186	$62.82	$62.80	$62.80
Purchase #7	$113.44	9.228%	$123.9082	$123.91	$123.90	$123.90
7 purchase totals =	$692.82		$749.1126	$749.12	$749.10	$749.00