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	$166.36	9.863%	$182.7681	$182.77	$182.75	$182.80
Purchase #2	$113.86	13.553%	$129.2914	$129.29	$129.30	$129.30
Purchase #3	$133.78	9.814%	$146.9092	$146.91	$146.90	$146.90
Purchase #4	$221.60	9.209%	$242.0071	$242.01	$242.00	$242.00
Purchase #5	$40.90	4.625%	$42.7916	$42.79	$42.80	$42.80
Purchase #6	$68.65	5.772%	$72.6125	$72.61	$72.60	$72.60
Purchase #7	$9.91	11.706%	$11.0701	$11.07	$11.05	$11.10
7 purchase totals =	$755.06		$827.4500	$827.45	$827.40	$827.50