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	$177.61	11.652%	$198.3051	$198.31	$198.30	$198.30
Purchase #2	$237.97	11.464%	$265.2509	$265.25	$265.25	$265.30
Purchase #3	$107.82	4.443%	$112.6104	$112.61	$112.60	$112.60
Purchase #4	$226.65	13.239%	$256.6562	$256.66	$256.65	$256.70
Purchase #5	$229.41	4.241%	$239.1393	$239.14	$239.15	$239.10
Purchase #6	$69.77	12.184%	$78.2708	$78.27	$78.25	$78.30
Purchase #7	$144.96	4.758%	$151.8572	$151.86	$151.85	$151.90
7 purchase totals =	$1,194.19		$1,302.0899	$1,302.10	$1,302.05	$1,302.20