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	$41.69	4.263%	$43.4672	$43.47	$43.45	$43.50
Purchase #2	$218.60	8.713%	$237.6466	$237.65	$237.65	$237.60
Purchase #3	$91.98	6.400%	$97.8667	$97.87	$97.85	$97.90
Purchase #4	$157.94	8.305%	$171.0569	$171.06	$171.05	$171.10
Purchase #5	$114.95	3.397%	$118.8549	$118.85	$118.85	$118.90
Purchase #6	$81.31	5.170%	$85.5137	$85.51	$85.50	$85.50
Purchase #7	$162.70	10.306%	$179.4679	$179.47	$179.45	$179.50
7 purchase totals =	$869.17		$933.8739	$933.88	$933.80	$934.00