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	$231.34	10.104%	$254.7146	$254.71	$254.70	$254.70
Purchase #2	$108.91	6.812%	$116.3289	$116.33	$116.35	$116.30
Purchase #3	$160.72	7.179%	$172.2581	$172.26	$172.25	$172.30
Purchase #4	$224.65	12.732%	$253.2524	$253.25	$253.25	$253.30
Purchase #5	$241.91	5.656%	$255.5924	$255.59	$255.60	$255.60
Purchase #6	$145.46	5.678%	$153.7192	$153.72	$153.70	$153.70
Purchase #7	$31.56	7.179%	$33.8257	$33.83	$33.85	$33.80
7 purchase totals =	$1,144.55		$1,239.6913	$1,239.69	$1,239.70	$1,239.70