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	$119.37	11.870%	$133.5392	$133.54	$133.55	$133.50
Purchase #2	$136.71	6.773%	$145.9694	$145.97	$145.95	$146.00
Purchase #3	$82.81	9.728%	$90.8658	$90.87	$90.85	$90.90
Purchase #4	$175.96	8.639%	$191.1612	$191.16	$191.15	$191.20
Purchase #5	$231.47	10.357%	$255.4433	$255.44	$255.45	$255.40
Purchase #6	$9.27	3.224%	$9.5689	$9.57	$9.55	$9.60
Purchase #7	$173.93	11.838%	$194.5198	$194.52	$194.50	$194.50
7 purchase totals =	$929.52		$1,021.0676	$1,021.07	$1,021.00	$1,021.10