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	$211.61	13.700%	$240.6006	$240.60	$240.60	$240.60
Purchase #2	$178.73	6.712%	$190.7264	$190.73	$190.75	$190.70
Purchase #3	$81.35	11.422%	$90.6418	$90.64	$90.65	$90.60
Purchase #4	$145.55	11.504%	$162.2941	$162.29	$162.30	$162.30
Purchase #5	$14.93	8.644%	$16.2205	$16.22	$16.20	$16.20
Purchase #6	$97.61	12.103%	$109.4237	$109.42	$109.40	$109.40
Purchase #7	$82.60	6.500%	$87.969	$87.97	$87.95	$88.00
7 purchase totals =	$812.38		$897.8761	$897.87	$897.85	$897.80