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	$56.45	5.487%	$59.5474	$59.55	$59.55	$59.50
Purchase #2	$117.89	4.400%	$123.0772	$123.08	$123.10	$123.10
Purchase #3	$54.45	4.360%	$56.824	$56.82	$56.80	$56.80
Purchase #4	$216.52	13.693%	$246.1681	$246.17	$246.15	$246.20
Purchase #5	$200.26	12.788%	$225.8692	$225.87	$225.85	$225.90
Purchase #6	$184.35	13.757%	$209.711	$209.71	$209.70	$209.70
Purchase #7	$240.64	6.431%	$256.1156	$256.12	$256.10	$256.10
7 purchase totals =	$1,070.56		$1,177.3125	$1,177.32	$1,177.25	$1,177.30