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	$130.95	10.230%	$144.3462	$144.35	$144.35	$144.30
Purchase #2	$95.75	5.328%	$100.8516	$100.85	$100.85	$100.90
Purchase #3	$230.81	13.504%	$261.9786	$261.98	$262.00	$262.00
Purchase #4	$48.34	11.411%	$53.8561	$53.86	$53.85	$53.90
Purchase #5	$9.79	5.442%	$10.3228	$10.32	$10.30	$10.30
Purchase #6	$160.92	5.213%	$169.3088	$169.31	$169.30	$169.30
Purchase #7	$237.51	13.313%	$269.1297	$269.13	$269.15	$269.10
7 purchase totals =	$914.07		$1,009.7938	$1,009.80	$1,009.80	$1,009.80