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	$177.93	8.265%	$192.6359	$192.64	$192.65	$192.60
Purchase #2	$211.51	12.466%	$237.8768	$237.88	$237.90	$237.90
Purchase #3	$52.61	5.553%	$55.5314	$55.53	$55.55	$55.50
Purchase #4	$81.90	10.175%	$90.2333	$90.23	$90.25	$90.20
Purchase #5	$181.75	5.815%	$192.3188	$192.32	$192.30	$192.30
Purchase #6	$181.48	7.154%	$194.4631	$194.46	$194.45	$194.50
Purchase #7	$42.39	10.575%	$46.8727	$46.87	$46.85	$46.90
7 purchase totals =	$929.57		$1,009.9320	$1,009.93	$1,009.95	$1,009.90