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	$229.58	9.138%	$250.559	$250.56	$250.55	$250.60
Purchase #2	$166.56	8.475%	$180.676	$180.68	$180.70	$180.70
Purchase #3	$81.60	11.181%	$90.7237	$90.72	$90.70	$90.70
Purchase #4	$85.57	5.537%	$90.308	$90.31	$90.30	$90.30
Purchase #5	$241.99	8.221%	$261.884	$261.88	$261.90	$261.90
Purchase #6	$172.32	9.409%	$188.5336	$188.53	$188.55	$188.50
Purchase #7	$201.30	11.559%	$224.5683	$224.57	$224.55	$224.60
7 purchase totals =	$1,178.92		$1,287.2526	$1,287.25	$1,287.25	$1,287.30