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	$98.45	9.264%	$107.5704	$107.57	$107.55	$107.60
Purchase #2	$50.73	8.602%	$55.0938	$55.09	$55.10	$55.10
Purchase #3	$25.86	11.142%	$28.7413	$28.74	$28.75	$28.70
Purchase #4	$134.79	7.823%	$145.3346	$145.33	$145.35	$145.30
Purchase #5	$38.56	13.821%	$43.8894	$43.89	$43.90	$43.90
Purchase #6	$144.93	12.189%	$162.5955	$162.60	$162.60	$162.60
Purchase #7	$19.46	5.182%	$20.4684	$20.47	$20.45	$20.50
7 purchase totals =	$512.78		$563.6934	$563.69	$563.70	$563.70