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	$197.46	12.616%	$222.3716	$222.37	$222.35	$222.40
Purchase #2	$138.94	3.706%	$144.0891	$144.09	$144.10	$144.10
Purchase #3	$247.52	6.284%	$263.0742	$263.07	$263.05	$263.10
Purchase #4	$126.60	12.790%	$142.7921	$142.79	$142.80	$142.80
Purchase #5	$225.60	8.796%	$245.4438	$245.44	$245.45	$245.40
Purchase #6	$148.89	13.534%	$169.0408	$169.04	$169.05	$169.00
Purchase #7	$108.80	4.312%	$113.4915	$113.49	$113.50	$113.50
7 purchase totals =	$1,193.81		$1,300.3031	$1,300.29	$1,300.30	$1,300.30