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	$246.66	3.670%	$255.7124	$255.71	$255.70	$255.70
Purchase #2	$18.41	5.746%	$19.4678	$19.47	$19.45	$19.50
Purchase #3	$114.32	8.314%	$123.8246	$123.82	$123.80	$123.80
Purchase #4	$114.72	7.674%	$123.5236	$123.52	$123.50	$123.50
Purchase #5	$223.28	3.118%	$230.2419	$230.24	$230.25	$230.20
Purchase #6	$58.42	12.656%	$65.8136	$65.81	$65.80	$65.80
Purchase #7	$206.67	7.202%	$221.5544	$221.55	$221.55	$221.60
7 purchase totals =	$982.48		$1,040.1383	$1,040.12	$1,040.05	$1,040.10