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	$96.34	8.790%	$104.8083	$104.81	$104.80	$104.80
Purchase #2	$59.60	3.472%	$61.6693	$61.67	$61.65	$61.70
Purchase #3	$41.67	8.531%	$45.2249	$45.22	$45.20	$45.20
Purchase #4	$118.28	13.312%	$134.0254	$134.03	$134.05	$134.00
Purchase #5	$134.85	7.850%	$145.4357	$145.44	$145.45	$145.40
Purchase #6	$120.76	5.390%	$127.269	$127.27	$127.25	$127.30
Purchase #7	$176.71	8.157%	$191.1242	$191.12	$191.10	$191.10
7 purchase totals =	$748.21		$809.5568	$809.56	$809.50	$809.50