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	$74.50	11.595%	$83.1383	$83.14	$83.15	$83.10
Purchase #2	$243.68	7.794%	$262.6724	$262.67	$262.65	$262.70
Purchase #3	$103.96	4.782%	$108.9314	$108.93	$108.95	$108.90
Purchase #4	$116.28	6.556%	$123.9033	$123.90	$123.90	$123.90
Purchase #5	$127.33	12.835%	$143.6728	$143.67	$143.65	$143.70
Purchase #6	$211.27	8.232%	$228.6617	$228.66	$228.65	$228.70
Purchase #7	$28.50	9.229%	$31.1303	$31.13	$31.15	$31.10
7 purchase totals =	$905.52		$982.1102	$982.10	$982.10	$982.10