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	$126.41	10.800%	$140.0623	$140.06	$140.05	$140.10
Purchase #2	$43.95	8.333%	$47.6124	$47.61	$47.60	$47.60
Purchase #3	$72.52	13.245%	$82.1253	$82.13	$82.15	$82.10
Purchase #4	$137.66	10.177%	$151.6697	$151.67	$151.65	$151.70
Purchase #5	$184.68	4.750%	$193.4523	$193.45	$193.45	$193.50
Purchase #6	$96.25	9.373%	$105.2715	$105.27	$105.25	$105.30
Purchase #7	$67.39	9.693%	$73.9221	$73.92	$73.90	$73.90
7 purchase totals =	$728.86		$794.1156	$794.11	$794.05	$794.20