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	$217.44	9.701%	$238.5339	$238.53	$238.55	$238.50
Purchase #2	$135.93	5.509%	$143.4184	$143.42	$143.40	$143.40
Purchase #3	$149.58	7.216%	$160.3737	$160.37	$160.35	$160.40
Purchase #4	$103.34	8.133%	$111.7446	$111.74	$111.75	$111.70
Purchase #5	$77.36	6.649%	$82.5037	$82.50	$82.50	$82.50
Purchase #6	$82.45	6.159%	$87.5281	$87.53	$87.55	$87.50
Purchase #7	$11.35	6.779%	$12.1194	$12.12	$12.10	$12.10
7 purchase totals =	$777.45		$836.2218	$836.21	$836.20	$836.10