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	$118.94	10.694%	$131.6594	$131.66	$131.65	$131.70
Purchase #2	$173.67	6.725%	$185.3493	$185.35	$185.35	$185.30
Purchase #3	$103.74	10.213%	$114.335	$114.34	$114.35	$114.30
Purchase #4	$90.79	10.767%	$100.5654	$100.57	$100.55	$100.60
Purchase #5	$154.57	4.406%	$161.3804	$161.38	$161.40	$161.40
Purchase #6	$186.85	11.233%	$207.8389	$207.84	$207.85	$207.80
Purchase #7	$175.43	3.178%	$181.0052	$181.01	$181.00	$181.00
7 purchase totals =	$1,003.99		$1,082.1336	$1,082.15	$1,082.15	$1,082.10