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	$151.85	4.221%	$158.2596	$158.26	$158.25	$158.30
Purchase #2	$174.64	5.668%	$184.5386	$184.54	$184.55	$184.50
Purchase #3	$123.93	4.586%	$129.6134	$129.61	$129.60	$129.60
Purchase #4	$33.34	8.381%	$36.1342	$36.13	$36.15	$36.10
Purchase #5	$172.62	13.630%	$196.1481	$196.15	$196.15	$196.10
Purchase #6	$31.70	5.359%	$33.3988	$33.40	$33.40	$33.40
Purchase #7	$113.72	10.209%	$125.3297	$125.33	$125.35	$125.30
7 purchase totals =	$801.80		$863.4224	$863.42	$863.45	$863.30