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	$114.92	11.113%	$127.6911	$127.69	$127.70	$127.70
Purchase #2	$114.72	4.396%	$119.7631	$119.76	$119.75	$119.80
Purchase #3	$249.56	10.806%	$276.5275	$276.53	$276.55	$276.50
Purchase #4	$188.84	4.167%	$196.709	$196.71	$196.70	$196.70
Purchase #5	$217.67	5.790%	$230.2731	$230.27	$230.25	$230.30
Purchase #6	$164.80	10.146%	$181.5206	$181.52	$181.50	$181.50
Purchase #7	$106.50	7.690%	$114.6899	$114.69	$114.70	$114.70
7 purchase totals =	$1,157.01		$1,247.1743	$1,247.17	$1,247.15	$1,247.20