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	$143.58	9.668%	$157.4613	$157.46	$157.45	$157.50
Purchase #2	$206.71	4.194%	$215.3794	$215.38	$215.40	$215.40
Purchase #3	$170.42	7.259%	$182.7908	$182.79	$182.80	$182.80
Purchase #4	$203.31	3.168%	$209.7509	$209.75	$209.75	$209.80
Purchase #5	$128.82	12.222%	$144.5644	$144.56	$144.55	$144.60
Purchase #6	$45.72	7.631%	$49.2089	$49.21	$49.20	$49.20
Purchase #7	$111.67	10.397%	$123.2803	$123.28	$123.30	$123.30
7 purchase totals =	$1,010.23		$1,082.4360	$1,082.43	$1,082.45	$1,082.60