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	$125.82	13.647%	$142.9907	$142.99	$143.00	$143.00
Purchase #2	$69.61	10.829%	$77.1481	$77.15	$77.15	$77.10
Purchase #3	$24.33	5.133%	$25.5789	$25.58	$25.60	$25.60
Purchase #4	$37.75	11.385%	$42.0478	$42.05	$42.05	$42.00
Purchase #5	$33.25	4.144%	$34.6279	$34.63	$34.65	$34.60
Purchase #6	$95.28	9.726%	$104.5469	$104.55	$104.55	$104.50
Purchase #7	$25.53	11.495%	$28.4647	$28.46	$28.45	$28.50
7 purchase totals =	$411.57		$455.4050	$455.41	$455.45	$455.30