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	$165.89	12.711%	$186.9763	$186.98	$187.00	$187.00
Purchase #2	$124.97	5.262%	$131.5459	$131.55	$131.55	$131.50
Purchase #3	$65.74	7.348%	$70.5706	$70.57	$70.55	$70.60
Purchase #4	$74.56	10.586%	$82.4529	$82.45	$82.45	$82.50
Purchase #5	$114.51	3.691%	$118.7366	$118.74	$118.75	$118.70
Purchase #6	$155.31	12.481%	$174.6942	$174.69	$174.70	$174.70
Purchase #7	$121.93	4.365%	$127.2522	$127.25	$127.25	$127.30
7 purchase totals =	$822.91		$892.2287	$892.23	$892.25	$892.30