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	$198.75	7.435%	$213.5271	$213.53	$213.55	$213.50
Purchase #2	$115.70	4.312%	$120.689	$120.69	$120.70	$120.70
Purchase #3	$166.86	12.577%	$187.846	$187.85	$187.85	$187.80
Purchase #4	$122.83	7.602%	$132.1675	$132.17	$132.15	$132.20
Purchase #5	$38.52	4.557%	$40.2754	$40.28	$40.30	$40.30
Purchase #6	$29.94	6.320%	$31.8322	$31.83	$31.85	$31.80
Purchase #7	$54.45	8.437%	$59.0439	$59.04	$59.05	$59.00
7 purchase totals =	$727.05		$785.3811	$785.39	$785.45	$785.30