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	$82.99	11.589%	$92.6077	$92.61	$92.60	$92.60
Purchase #2	$18.64	4.571%	$19.492	$19.49	$19.50	$19.50
Purchase #3	$71.45	9.252%	$78.0606	$78.06	$78.05	$78.10
Purchase #4	$10.68	10.646%	$11.817	$11.82	$11.80	$11.80
Purchase #5	$11.41	6.228%	$12.1206	$12.12	$12.10	$12.10
Purchase #6	$196.38	13.384%	$222.6635	$222.66	$222.65	$222.70
Purchase #7	$240.57	9.872%	$264.3191	$264.32	$264.30	$264.30
7 purchase totals =	$632.12		$701.0805	$701.08	$701.00	$701.10