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	$73.65	11.514%	$82.1301	$82.13	$82.15	$82.10
Purchase #2	$221.96	5.123%	$233.331	$233.33	$233.35	$233.30
Purchase #3	$127.67	11.704%	$142.6125	$142.61	$142.60	$142.60
Purchase #4	$202.98	8.152%	$219.5269	$219.53	$219.55	$219.50
Purchase #5	$153.87	12.288%	$172.7775	$172.78	$172.80	$172.80
Purchase #6	$13.42	12.524%	$15.1007	$15.10	$15.10	$15.10
Purchase #7	$135.90	5.465%	$143.3269	$143.33	$143.35	$143.30
7 purchase totals =	$929.45		$1,008.8056	$1,008.81	$1,008.90	$1,008.70