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	$99.76	11.416%	$111.1486	$111.15	$111.15	$111.10
Purchase #2	$64.76	11.295%	$72.0746	$72.07	$72.05	$72.10
Purchase #3	$36.70	6.745%	$39.1754	$39.18	$39.20	$39.20
Purchase #4	$217.60	3.549%	$225.3226	$225.32	$225.30	$225.30
Purchase #5	$250.81	8.447%	$271.9959	$272.00	$272.00	$272.00
Purchase #6	$186.37	5.324%	$196.2923	$196.29	$196.30	$196.30
Purchase #7	$14.54	3.859%	$15.1011	$15.10	$15.10	$15.10
7 purchase totals =	$870.54		$931.1105	$931.11	$931.10	$931.10