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	$163.41	13.289%	$185.1256	$185.13	$185.15	$185.10
Purchase #2	$139.50	6.610%	$148.721	$148.72	$148.70	$148.70
Purchase #3	$21.33	8.831%	$23.2137	$23.21	$23.20	$23.20
Purchase #4	$100.71	10.253%	$111.0358	$111.04	$111.05	$111.00
Purchase #5	$237.60	11.798%	$265.632	$265.63	$265.65	$265.60
Purchase #6	$181.43	5.494%	$191.3978	$191.40	$191.40	$191.40
Purchase #7	$160.51	11.203%	$178.4919	$178.49	$178.50	$178.50
7 purchase totals =	$1,004.49		$1,103.6178	$1,103.62	$1,103.65	$1,103.50