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	$117.80	13.666%	$133.8985	$133.90	$133.90	$133.90
Purchase #2	$103.58	7.555%	$111.4055	$111.41	$111.40	$111.40
Purchase #3	$211.35	7.333%	$226.8483	$226.85	$226.85	$226.80
Purchase #4	$217.49	3.724%	$225.5893	$225.59	$225.60	$225.60
Purchase #5	$47.93	12.114%	$53.7362	$53.74	$53.75	$53.70
Purchase #6	$178.77	11.470%	$199.2749	$199.27	$199.25	$199.30
Purchase #7	$83.42	3.662%	$86.4748	$86.47	$86.45	$86.50
7 purchase totals =	$960.34		$1,037.2275	$1,037.23	$1,037.20	$1,037.20