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	$224.71	4.732%	$235.3433	$235.34	$235.35	$235.30
Purchase #2	$137.55	5.825%	$145.5623	$145.56	$145.55	$145.60
Purchase #3	$145.56	5.840%	$154.0607	$154.06	$154.05	$154.10
Purchase #4	$59.81	13.358%	$67.7994	$67.80	$67.80	$67.80
Purchase #5	$166.49	13.600%	$189.1326	$189.13	$189.15	$189.10
Purchase #6	$102.65	13.344%	$116.3476	$116.35	$116.35	$116.30
Purchase #7	$82.64	9.418%	$90.423	$90.42	$90.40	$90.40
7 purchase totals =	$919.41		$998.6689	$998.66	$998.65	$998.60