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	$134.29	3.800%	$139.393	$139.39	$139.40	$139.40
Purchase #2	$135.79	5.423%	$143.1539	$143.15	$143.15	$143.20
Purchase #3	$172.99	3.156%	$178.4496	$178.45	$178.45	$178.40
Purchase #4	$84.76	9.129%	$92.4977	$92.50	$92.50	$92.50
Purchase #5	$144.68	7.477%	$155.4977	$155.50	$155.50	$155.50
Purchase #6	$127.75	13.599%	$145.1227	$145.12	$145.10	$145.10
Purchase #7	$188.78	11.469%	$210.4312	$210.43	$210.45	$210.40
7 purchase totals =	$989.04		$1,064.5458	$1,064.54	$1,064.55	$1,064.50