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	$75.93	9.184%	$82.9034	$82.90	$82.90	$82.90
Purchase #2	$137.69	9.222%	$150.3878	$150.39	$150.40	$150.40
Purchase #3	$117.56	7.371%	$126.2253	$126.23	$126.25	$126.20
Purchase #4	$189.85	4.274%	$197.9642	$197.96	$197.95	$198.00
Purchase #5	$151.97	9.479%	$166.3752	$166.38	$166.40	$166.40
Purchase #6	$187.25	9.634%	$205.2897	$205.29	$205.30	$205.30
Purchase #7	$83.77	7.493%	$90.0469	$90.05	$90.05	$90.00
7 purchase totals =	$944.02		$1,019.1925	$1,019.20	$1,019.25	$1,019.20