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	$233.55	11.502%	$260.4129	$260.41	$260.40	$260.40
Purchase #2	$167.59	3.545%	$173.5311	$173.53	$173.55	$173.50
Purchase #3	$126.27	12.721%	$142.3328	$142.33	$142.35	$142.30
Purchase #4	$166.66	11.329%	$185.5409	$185.54	$185.55	$185.50
Purchase #5	$49.92	8.577%	$54.2016	$54.20	$54.20	$54.20
Purchase #6	$207.79	9.111%	$226.7217	$226.72	$226.70	$226.70
Purchase #7	$35.68	8.464%	$38.7	$38.70	$38.70	$38.70
7 purchase totals =	$987.46		$1,081.4410	$1,081.43	$1,081.45	$1,081.30