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	$232.95	12.601%	$262.304	$262.30	$262.30	$262.30
Purchase #2	$208.71	11.603%	$232.9266	$232.93	$232.95	$232.90
Purchase #3	$73.62	13.797%	$83.7774	$83.78	$83.80	$83.80
Purchase #4	$114.71	7.699%	$123.5415	$123.54	$123.55	$123.50
Purchase #5	$203.92	8.594%	$221.4449	$221.44	$221.45	$221.40
Purchase #6	$91.95	8.181%	$99.4724	$99.47	$99.45	$99.50
Purchase #7	$234.78	11.802%	$262.4887	$262.49	$262.50	$262.50
7 purchase totals =	$1,160.64		$1,285.9555	$1,285.95	$1,286.00	$1,285.90