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	$241.46	5.336%	$254.3443	$254.34	$254.35	$254.30
Purchase #2	$136.52	5.664%	$144.2525	$144.25	$144.25	$144.30
Purchase #3	$54.37	12.804%	$61.3315	$61.33	$61.35	$61.30
Purchase #4	$99.59	3.502%	$103.0776	$103.08	$103.10	$103.10
Purchase #5	$95.91	5.119%	$100.8196	$100.82	$100.80	$100.80
Purchase #6	$48.37	8.231%	$52.3513	$52.35	$52.35	$52.40
Purchase #7	$151.70	5.652%	$160.2741	$160.27	$160.25	$160.30
7 purchase totals =	$827.92		$876.4509	$876.44	$876.45	$876.50