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	$44.76	7.743%	$48.2258	$48.23	$48.25	$48.20
Purchase #2	$73.62	3.404%	$76.126	$76.13	$76.15	$76.10
Purchase #3	$85.38	5.508%	$90.0827	$90.08	$90.10	$90.10
Purchase #4	$56.78	11.623%	$63.3795	$63.38	$63.40	$63.40
Purchase #5	$102.84	8.594%	$111.6781	$111.68	$111.70	$111.70
Purchase #6	$112.86	13.254%	$127.8185	$127.82	$127.80	$127.80
Purchase #7	$66.92	8.809%	$72.815	$72.82	$72.80	$72.80
7 purchase totals =	$543.16		$590.1256	$590.14	$590.20	$590.10