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	$149.78	5.806%	$158.4762	$158.48	$158.50	$158.50
Purchase #2	$134.56	6.683%	$143.5526	$143.55	$143.55	$143.60
Purchase #3	$80.43	6.485%	$85.6459	$85.65	$85.65	$85.60
Purchase #4	$239.34	12.645%	$269.6045	$269.60	$269.60	$269.60
Purchase #5	$104.34	11.745%	$116.5947	$116.59	$116.60	$116.60
Purchase #6	$185.26	12.567%	$208.5416	$208.54	$208.55	$208.50
Purchase #7	$132.48	5.444%	$139.6922	$139.69	$139.70	$139.70
7 purchase totals =	$1,026.19		$1,122.1077	$1,122.10	$1,122.15	$1,122.10