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	$204.56	6.459%	$217.7725	$217.77	$217.75	$217.80
Purchase #2	$177.42	4.617%	$185.6115	$185.61	$185.60	$185.60
Purchase #3	$115.66	10.231%	$127.4932	$127.49	$127.50	$127.50
Purchase #4	$145.46	9.705%	$159.5769	$159.58	$159.60	$159.60
Purchase #5	$215.45	4.124%	$224.3352	$224.34	$224.35	$224.30
Purchase #6	$78.48	10.813%	$86.966	$86.97	$86.95	$87.00
Purchase #7	$47.28	5.782%	$50.0137	$50.01	$50.00	$50.00
7 purchase totals =	$984.31		$1,051.7690	$1,051.77	$1,051.75	$1,051.80