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	$141.41	6.324%	$150.3528	$150.35	$150.35	$150.40
Purchase #2	$151.97	6.541%	$161.9104	$161.91	$161.90	$161.90
Purchase #3	$37.87	9.708%	$41.5464	$41.55	$41.55	$41.50
Purchase #4	$197.92	9.859%	$217.4329	$217.43	$217.45	$217.40
Purchase #5	$89.42	8.425%	$96.9536	$96.95	$96.95	$97.00
Purchase #6	$89.51	13.800%	$101.8624	$101.86	$101.85	$101.90
Purchase #7	$80.29	12.846%	$90.6041	$90.60	$90.60	$90.60
7 purchase totals =	$788.39		$860.6626	$860.65	$860.65	$860.70