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	$154.58	4.243%	$161.1388	$161.14	$161.15	$161.10
Purchase #2	$86.49	3.528%	$89.5414	$89.54	$89.55	$89.50
Purchase #3	$142.95	13.619%	$162.4184	$162.42	$162.40	$162.40
Purchase #4	$203.72	6.169%	$216.2875	$216.29	$216.30	$216.30
Purchase #5	$225.32	13.323%	$255.3394	$255.34	$255.35	$255.30
Purchase #6	$75.32	9.390%	$82.3925	$82.39	$82.40	$82.40
Purchase #7	$26.61	10.703%	$29.4581	$29.46	$29.45	$29.50
7 purchase totals =	$914.99		$996.5761	$996.58	$996.60	$996.50