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	$228.64	8.402%	$247.8503	$247.85	$247.85	$247.90
Purchase #2	$80.30	8.134%	$86.8316	$86.83	$86.85	$86.80
Purchase #3	$165.91	6.458%	$176.6245	$176.62	$176.60	$176.60
Purchase #4	$81.45	11.138%	$90.5219	$90.52	$90.50	$90.50
Purchase #5	$73.37	7.384%	$78.7876	$78.79	$78.80	$78.80
Purchase #6	$208.57	8.358%	$226.0023	$226.00	$226.00	$226.00
Purchase #7	$87.45	7.613%	$94.1076	$94.11	$94.10	$94.10
7 purchase totals =	$925.69		$1,000.7258	$1,000.72	$1,000.70	$1,000.70