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	$168.74	3.861%	$175.2551	$175.26	$175.25	$175.30
Purchase #2	$77.41	3.348%	$80.0017	$80.00	$80.00	$80.00
Purchase #3	$197.64	12.451%	$222.2482	$222.25	$222.25	$222.20
Purchase #4	$73.92	11.864%	$82.6899	$82.69	$82.70	$82.70
Purchase #5	$140.80	12.500%	$158.4	$158.40	$158.40	$158.40
Purchase #6	$91.78	3.844%	$95.308	$95.31	$95.30	$95.30
Purchase #7	$139.27	12.453%	$156.6133	$156.61	$156.60	$156.60
7 purchase totals =	$889.56		$970.5162	$970.52	$970.50	$970.50