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	$216.46	9.121%	$236.2033	$236.20	$236.20	$236.20
Purchase #2	$189.69	8.153%	$205.1554	$205.16	$205.15	$205.20
Purchase #3	$100.99	10.596%	$111.6909	$111.69	$111.70	$111.70
Purchase #4	$166.29	11.789%	$185.8939	$185.89	$185.90	$185.90
Purchase #5	$83.98	7.829%	$90.5548	$90.55	$90.55	$90.60
Purchase #6	$115.44	13.341%	$130.8409	$130.84	$130.85	$130.80
Purchase #7	$138.93	11.620%	$155.0737	$155.07	$155.05	$155.10
7 purchase totals =	$1,011.78		$1,115.4129	$1,115.40	$1,115.40	$1,115.50