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	$231.68	4.800%	$242.8006	$242.80	$242.80	$242.80
Purchase #2	$99.53	6.206%	$105.7068	$105.71	$105.70	$105.70
Purchase #3	$126.69	11.707%	$141.5216	$141.52	$141.50	$141.50
Purchase #4	$164.60	12.405%	$185.0186	$185.02	$185.00	$185.00
Purchase #5	$183.42	13.745%	$208.6311	$208.63	$208.65	$208.60
Purchase #6	$178.25	10.342%	$196.6846	$196.68	$196.70	$196.70
Purchase #7	$98.57	10.425%	$108.8459	$108.85	$108.85	$108.80
7 purchase totals =	$1,082.74		$1,189.2092	$1,189.21	$1,189.20	$1,189.10