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	$92.96	11.506%	$103.656	$103.66	$103.65	$103.70
Purchase #2	$228.86	3.857%	$237.6871	$237.69	$237.70	$237.70
Purchase #3	$105.51	6.235%	$112.0885	$112.09	$112.10	$112.10
Purchase #4	$165.92	11.787%	$185.477	$185.48	$185.50	$185.50
Purchase #5	$104.81	3.591%	$108.5737	$108.57	$108.55	$108.60
Purchase #6	$83.60	7.819%	$90.1367	$90.14	$90.15	$90.10
Purchase #7	$196.30	4.513%	$205.159	$205.16	$205.15	$205.20
7 purchase totals =	$977.96		$1,042.7780	$1,042.79	$1,042.80	$1,042.90