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	$174.94	12.335%	$196.5188	$196.52	$196.50	$196.50
Purchase #2	$42.97	5.711%	$45.424	$45.42	$45.40	$45.40
Purchase #3	$50.83	10.852%	$56.3461	$56.35	$56.35	$56.30
Purchase #4	$147.35	3.870%	$153.0524	$153.05	$153.05	$153.10
Purchase #5	$250.51	6.522%	$266.8483	$266.85	$266.85	$266.80
Purchase #6	$119.74	9.338%	$130.9213	$130.92	$130.90	$130.90
Purchase #7	$87.25	8.567%	$94.7247	$94.72	$94.70	$94.70
7 purchase totals =	$873.59		$943.8356	$943.83	$943.75	$943.70