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	$209.56	9.682%	$229.8496	$229.85	$229.85	$229.80
Purchase #2	$120.85	5.364%	$127.3324	$127.33	$127.35	$127.30
Purchase #3	$116.63	9.797%	$128.0562	$128.06	$128.05	$128.10
Purchase #4	$101.41	4.381%	$105.8528	$105.85	$105.85	$105.90
Purchase #5	$194.27	7.160%	$208.1797	$208.18	$208.20	$208.20
Purchase #6	$89.77	6.536%	$95.6374	$95.64	$95.65	$95.60
Purchase #7	$197.76	3.204%	$204.0962	$204.10	$204.10	$204.10
7 purchase totals =	$1,030.25		$1,099.0043	$1,099.01	$1,099.05	$1,099.00