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	$208.52	11.210%	$231.8951	$231.90	$231.90	$231.90
Purchase #2	$37.51	6.430%	$39.9219	$39.92	$39.90	$39.90
Purchase #3	$19.42	4.323%	$20.2595	$20.26	$20.25	$20.30
Purchase #4	$51.42	9.841%	$56.4802	$56.48	$56.50	$56.50
Purchase #5	$243.40	9.451%	$266.4037	$266.40	$266.40	$266.40
Purchase #6	$233.64	8.786%	$254.1676	$254.17	$254.15	$254.20
Purchase #7	$154.38	5.133%	$162.3043	$162.30	$162.30	$162.30
7 purchase totals =	$948.29		$1,031.4323	$1,031.43	$1,031.40	$1,031.50