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	$13.34	9.309%	$14.5818	$14.58	$14.60	$14.60
Purchase #2	$96.94	3.499%	$100.3319	$100.33	$100.35	$100.30
Purchase #3	$143.84	8.489%	$156.0506	$156.05	$156.05	$156.10
Purchase #4	$143.95	10.138%	$158.5437	$158.54	$158.55	$158.50
Purchase #5	$56.52	3.442%	$58.4654	$58.47	$58.45	$58.50
Purchase #6	$98.95	4.476%	$103.379	$103.38	$103.40	$103.40
Purchase #7	$71.27	8.231%	$77.1362	$77.14	$77.15	$77.10
7 purchase totals =	$624.81		$668.4886	$668.49	$668.55	$668.50