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	$181.82	12.387%	$204.342	$204.34	$204.35	$204.30
Purchase #2	$230.27	4.560%	$240.7703	$240.77	$240.75	$240.80
Purchase #3	$160.72	6.873%	$171.7663	$171.77	$171.75	$171.80
Purchase #4	$115.50	6.828%	$123.3863	$123.39	$123.40	$123.40
Purchase #5	$13.83	5.481%	$14.588	$14.59	$14.60	$14.60
Purchase #6	$84.67	5.317%	$89.1719	$89.17	$89.15	$89.20
Purchase #7	$241.45	5.597%	$254.964	$254.96	$254.95	$255.00
7 purchase totals =	$1,028.26		$1,098.9888	$1,098.99	$1,098.95	$1,099.10