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	$242.94	4.589%	$254.0885	$254.09	$254.10	$254.10
Purchase #2	$104.25	13.225%	$118.0371	$118.04	$118.05	$118.00
Purchase #3	$202.93	9.714%	$222.6426	$222.64	$222.65	$222.60
Purchase #4	$164.35	10.272%	$181.232	$181.23	$181.25	$181.20
Purchase #5	$25.48	7.829%	$27.4748	$27.47	$27.45	$27.50
Purchase #6	$211.75	11.220%	$235.5084	$235.51	$235.50	$235.50
Purchase #7	$59.53	4.605%	$62.2714	$62.27	$62.25	$62.30
7 purchase totals =	$1,011.23		$1,101.2548	$1,101.25	$1,101.25	$1,101.20