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	$133.60	7.731%	$143.9286	$143.93	$143.95	$143.90
Purchase #2	$130.39	7.121%	$139.6751	$139.68	$139.70	$139.70
Purchase #3	$172.71	6.219%	$183.4508	$183.45	$183.45	$183.50
Purchase #4	$92.51	10.418%	$102.1477	$102.15	$102.15	$102.10
Purchase #5	$222.33	4.286%	$231.8591	$231.86	$231.85	$231.90
Purchase #6	$37.89	12.330%	$42.5618	$42.56	$42.55	$42.60
Purchase #7	$237.59	8.307%	$257.3266	$257.33	$257.35	$257.30
7 purchase totals =	$1,027.02		$1,100.9497	$1,100.96	$1,101.00	$1,101.00