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	$106.51	11.592%	$118.8566	$118.86	$118.85	$118.90
Purchase #2	$63.66	13.583%	$72.3069	$72.31	$72.30	$72.30
Purchase #3	$138.43	5.506%	$146.052	$146.05	$146.05	$146.10
Purchase #4	$221.27	10.208%	$243.8572	$243.86	$243.85	$243.90
Purchase #5	$54.63	11.414%	$60.8655	$60.87	$60.85	$60.90
Purchase #6	$105.51	12.152%	$118.3316	$118.33	$118.35	$118.30
Purchase #7	$40.81	8.479%	$44.2703	$44.27	$44.25	$44.30
7 purchase totals =	$730.82		$804.5401	$804.55	$804.50	$804.70