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	$185.69	12.484%	$208.8715	$208.87	$208.85	$208.90
Purchase #2	$77.92	6.753%	$83.1819	$83.18	$83.20	$83.20
Purchase #3	$119.47	4.268%	$124.569	$124.57	$124.55	$124.60
Purchase #4	$46.32	10.268%	$51.0761	$51.08	$51.10	$51.10
Purchase #5	$241.68	8.578%	$262.4113	$262.41	$262.40	$262.40
Purchase #6	$79.25	3.622%	$82.1204	$82.12	$82.10	$82.10
Purchase #7	$236.83	4.781%	$248.1528	$248.15	$248.15	$248.20
7 purchase totals =	$987.16		$1,060.3830	$1,060.38	$1,060.35	$1,060.50