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	$236.85	7.608%	$254.8695	$254.87	$254.85	$254.90
Purchase #2	$237.96	10.242%	$262.3319	$262.33	$262.35	$262.30
Purchase #3	$129.99	12.262%	$145.9294	$145.93	$145.95	$145.90
Purchase #4	$118.92	6.351%	$126.4726	$126.47	$126.45	$126.50
Purchase #5	$65.89	9.425%	$72.1001	$72.10	$72.10	$72.10
Purchase #6	$99.34	12.863%	$112.1181	$112.12	$112.10	$112.10
Purchase #7	$78.92	5.344%	$83.1375	$83.14	$83.15	$83.10
7 purchase totals =	$967.87		$1,056.9591	$1,056.96	$1,056.95	$1,056.90