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	$99.71	5.643%	$105.3366	$105.34	$105.35	$105.30
Purchase #2	$154.92	4.817%	$162.3825	$162.38	$162.40	$162.40
Purchase #3	$117.39	13.803%	$133.5933	$133.59	$133.60	$133.60
Purchase #4	$149.60	11.862%	$167.3456	$167.35	$167.35	$167.30
Purchase #5	$87.88	13.140%	$99.4274	$99.43	$99.45	$99.40
Purchase #6	$43.77	6.367%	$46.5568	$46.56	$46.55	$46.60
Purchase #7	$238.74	7.436%	$256.4927	$256.49	$256.50	$256.50
7 purchase totals =	$892.01		$971.1349	$971.14	$971.20	$971.10