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	$133.87	8.170%	$144.8072	$144.81	$144.80	$144.80
Purchase #2	$223.77	3.434%	$231.4543	$231.45	$231.45	$231.50
Purchase #3	$136.55	13.728%	$155.2956	$155.30	$155.30	$155.30
Purchase #4	$134.97	3.366%	$139.5131	$139.51	$139.50	$139.50
Purchase #5	$57.34	8.349%	$62.1273	$62.13	$62.15	$62.10
Purchase #6	$230.45	7.814%	$248.4574	$248.46	$248.45	$248.50
Purchase #7	$209.87	11.409%	$233.8141	$233.81	$233.80	$233.80
7 purchase totals =	$1,126.82		$1,215.4690	$1,215.47	$1,215.45	$1,215.50