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	$101.68	3.259%	$104.9938	$104.99	$105.00	$105.00
Purchase #2	$145.41	13.774%	$165.4388	$165.44	$165.45	$165.40
Purchase #3	$95.97	7.725%	$103.3837	$103.38	$103.40	$103.40
Purchase #4	$169.65	11.180%	$188.6169	$188.62	$188.60	$188.60
Purchase #5	$149.56	8.622%	$162.4551	$162.46	$162.45	$162.50
Purchase #6	$185.67	13.688%	$211.0845	$211.08	$211.10	$211.10
Purchase #7	$130.97	5.258%	$137.8564	$137.86	$137.85	$137.90
7 purchase totals =	$978.91		$1,073.8292	$1,073.83	$1,073.85	$1,073.90