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	$112.62	4.851%	$118.0832	$118.08	$118.10	$118.10
Purchase #2	$179.51	11.548%	$200.2398	$200.24	$200.25	$200.20
Purchase #3	$118.59	8.217%	$128.3345	$128.33	$128.35	$128.30
Purchase #4	$133.43	4.196%	$139.0287	$139.03	$139.05	$139.00
Purchase #5	$43.51	3.867%	$45.1925	$45.19	$45.20	$45.20
Purchase #6	$238.50	12.523%	$268.3674	$268.37	$268.35	$268.40
Purchase #7	$121.66	6.546%	$129.6239	$129.62	$129.60	$129.60
7 purchase totals =	$947.82		$1,028.8700	$1,028.86	$1,028.90	$1,028.80