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	$181.67	7.161%	$194.6794	$194.68	$194.70	$194.70
Purchase #2	$74.84	4.616%	$78.2946	$78.29	$78.30	$78.30
Purchase #3	$132.71	5.465%	$139.9626	$139.96	$139.95	$140.00
Purchase #4	$104.82	6.714%	$111.8576	$111.86	$111.85	$111.90
Purchase #5	$6.42	9.627%	$7.0381	$7.04	$7.05	$7.00
Purchase #6	$142.86	5.727%	$151.0416	$151.04	$151.05	$151.00
Purchase #7	$6.93	6.741%	$7.3972	$7.40	$7.40	$7.40
7 purchase totals =	$650.25		$690.2711	$690.27	$690.30	$690.30