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	$237.81	4.227%	$247.8622	$247.86	$247.85	$247.90
Purchase #2	$86.97	3.137%	$89.6982	$89.70	$89.70	$89.70
Purchase #3	$35.98	10.403%	$39.723	$39.72	$39.70	$39.70
Purchase #4	$194.57	7.430%	$209.0266	$209.03	$209.05	$209.00
Purchase #5	$78.96	13.159%	$89.3503	$89.35	$89.35	$89.40
Purchase #6	$166.88	5.836%	$176.6191	$176.62	$176.60	$176.60
Purchase #7	$103.59	4.240%	$107.9822	$107.98	$108.00	$108.00
7 purchase totals =	$904.76		$960.2616	$960.26	$960.25	$960.30