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	$179.82	11.551%	$200.591	$200.59	$200.60	$200.60
Purchase #2	$145.79	13.641%	$165.6772	$165.68	$165.70	$165.70
Purchase #3	$20.64	4.836%	$21.6382	$21.64	$21.65	$21.60
Purchase #4	$221.38	13.516%	$251.3017	$251.30	$251.30	$251.30
Purchase #5	$71.56	8.202%	$77.4294	$77.43	$77.45	$77.40
Purchase #6	$214.33	3.803%	$222.481	$222.48	$222.50	$222.50
Purchase #7	$95.83	6.725%	$102.2746	$102.27	$102.25	$102.30
7 purchase totals =	$949.35		$1,041.3931	$1,041.39	$1,041.45	$1,041.40