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	$215.58	11.525%	$240.4256	$240.43	$240.45	$240.40
Purchase #2	$185.88	10.518%	$205.4309	$205.43	$205.45	$205.40
Purchase #3	$143.87	12.757%	$162.2235	$162.22	$162.20	$162.20
Purchase #4	$124.45	4.704%	$130.3041	$130.30	$130.30	$130.30
Purchase #5	$84.29	11.766%	$94.2076	$94.21	$94.20	$94.20
Purchase #6	$53.30	12.397%	$59.9076	$59.91	$59.90	$59.90
Purchase #7	$94.73	13.808%	$107.8103	$107.81	$107.80	$107.80
7 purchase totals =	$902.10		$1,000.3096	$1,000.31	$1,000.30	$1,000.20