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	$91.49	13.184%	$103.552	$103.55	$103.55	$103.60
Purchase #2	$117.94	5.277%	$124.1637	$124.16	$124.15	$124.20
Purchase #3	$142.51	7.541%	$153.2567	$153.26	$153.25	$153.30
Purchase #4	$202.92	9.758%	$222.7209	$222.72	$222.70	$222.70
Purchase #5	$187.89	9.584%	$205.8974	$205.90	$205.90	$205.90
Purchase #6	$163.55	5.599%	$172.7072	$172.71	$172.70	$172.70
Purchase #7	$36.44	5.473%	$38.4344	$38.43	$38.45	$38.40
7 purchase totals =	$942.74		$1,020.7323	$1,020.73	$1,020.70	$1,020.80