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	$52.46	13.351%	$59.4639	$59.46	$59.45	$59.50
Purchase #2	$237.96	8.187%	$257.4418	$257.44	$257.45	$257.40
Purchase #3	$52.29	3.861%	$54.3089	$54.31	$54.30	$54.30
Purchase #4	$51.64	3.593%	$53.4954	$53.50	$53.50	$53.50
Purchase #5	$196.28	12.387%	$220.5932	$220.59	$220.60	$220.60
Purchase #6	$130.76	6.742%	$139.5758	$139.58	$139.60	$139.60
Purchase #7	$34.93	7.467%	$37.5382	$37.54	$37.55	$37.50
7 purchase totals =	$756.32		$822.4172	$822.42	$822.45	$822.40