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	$164.96	5.440%	$173.9338	$173.93	$173.95	$173.90
Purchase #2	$246.49	9.537%	$269.9978	$270.00	$270.00	$270.00
Purchase #3	$48.32	11.577%	$53.914	$53.91	$53.90	$53.90
Purchase #4	$103.42	11.552%	$115.3671	$115.37	$115.35	$115.40
Purchase #5	$98.90	13.191%	$111.9459	$111.95	$111.95	$111.90
Purchase #6	$18.45	6.411%	$19.6328	$19.63	$19.65	$19.60
Purchase #7	$166.71	11.392%	$185.7016	$185.70	$185.70	$185.70
7 purchase totals =	$847.25		$930.4930	$930.49	$930.50	$930.40