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	$182.38	3.274%	$188.3511	$188.35	$188.35	$188.40
Purchase #2	$41.92	10.297%	$46.2365	$46.24	$46.25	$46.20
Purchase #3	$172.83	3.607%	$179.064	$179.06	$179.05	$179.10
Purchase #4	$54.60	11.412%	$60.831	$60.83	$60.85	$60.80
Purchase #5	$164.52	10.453%	$181.7173	$181.72	$181.70	$181.70
Purchase #6	$84.35	3.714%	$87.4828	$87.48	$87.50	$87.50
Purchase #7	$133.43	6.806%	$142.5112	$142.51	$142.50	$142.50
7 purchase totals =	$834.03		$886.1939	$886.19	$886.20	$886.20