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	$196.35	4.541%	$205.2663	$205.27	$205.25	$205.30
Purchase #2	$14.90	6.664%	$15.8929	$15.89	$15.90	$15.90
Purchase #3	$62.33	13.501%	$70.7452	$70.75	$70.75	$70.70
Purchase #4	$84.54	7.523%	$90.8999	$90.90	$90.90	$90.90
Purchase #5	$220.43	8.427%	$239.0056	$239.01	$239.00	$239.00
Purchase #6	$52.70	13.589%	$59.8614	$59.86	$59.85	$59.90
Purchase #7	$88.67	7.813%	$95.5978	$95.60	$95.60	$95.60
7 purchase totals =	$719.92		$777.2691	$777.28	$777.25	$777.30