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	$83.57	5.275%	$87.9783	$87.98	$88.00	$88.00
Purchase #2	$46.60	10.425%	$51.4581	$51.46	$51.45	$51.50
Purchase #3	$118.55	10.575%	$131.0867	$131.09	$131.10	$131.10
Purchase #4	$57.75	13.724%	$65.6756	$65.68	$65.70	$65.70
Purchase #5	$103.30	8.817%	$112.408	$112.41	$112.40	$112.40
Purchase #6	$130.46	6.712%	$139.2165	$139.22	$139.20	$139.20
Purchase #7	$192.36	8.375%	$208.4702	$208.47	$208.45	$208.50
7 purchase totals =	$732.59		$796.2934	$796.31	$796.30	$796.40