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	$23.45	4.330%	$24.4654	$24.47	$24.45	$24.50
Purchase #2	$85.43	4.806%	$89.5358	$89.54	$89.55	$89.50
Purchase #3	$43.93	5.285%	$46.2517	$46.25	$46.25	$46.30
Purchase #4	$137.69	6.792%	$147.0419	$147.04	$147.05	$147.00
Purchase #5	$155.82	6.341%	$165.7005	$165.70	$165.70	$165.70
Purchase #6	$97.82	6.419%	$104.0991	$104.10	$104.10	$104.10
Purchase #7	$83.88	13.483%	$95.1895	$95.19	$95.20	$95.20
7 purchase totals =	$628.02		$672.2839	$672.29	$672.30	$672.30