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	$182.75	6.264%	$194.1975	$194.20	$194.20	$194.20
Purchase #2	$117.77	8.178%	$127.4012	$127.40	$127.40	$127.40
Purchase #3	$208.70	10.719%	$231.0706	$231.07	$231.05	$231.10
Purchase #4	$68.53	11.831%	$76.6378	$76.64	$76.65	$76.60
Purchase #5	$79.78	11.726%	$89.135	$89.14	$89.15	$89.10
Purchase #6	$23.44	4.598%	$24.5178	$24.52	$24.50	$24.50
Purchase #7	$168.82	9.762%	$185.3002	$185.30	$185.30	$185.30
7 purchase totals =	$849.79		$928.2601	$928.27	$928.25	$928.20