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	$144.76	10.422%	$159.8469	$159.85	$159.85	$159.80
Purchase #2	$100.80	3.200%	$104.0256	$104.03	$104.05	$104.00
Purchase #3	$37.57	7.259%	$40.2972	$40.30	$40.30	$40.30
Purchase #4	$138.83	8.823%	$151.079	$151.08	$151.10	$151.10
Purchase #5	$169.47	10.643%	$187.5067	$187.51	$187.50	$187.50
Purchase #6	$156.90	11.235%	$174.5277	$174.53	$174.55	$174.50
Purchase #7	$160.38	10.309%	$176.9136	$176.91	$176.90	$176.90
7 purchase totals =	$908.71		$994.1967	$994.21	$994.25	$994.10