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	$102.46	6.527%	$109.1476	$109.15	$109.15	$109.10
Purchase #2	$239.86	6.641%	$255.7891	$255.79	$255.80	$255.80
Purchase #3	$107.94	3.557%	$111.7794	$111.78	$111.80	$111.80
Purchase #4	$166.75	9.435%	$182.4829	$182.48	$182.50	$182.50
Purchase #5	$178.84	4.205%	$186.3602	$186.36	$186.35	$186.40
Purchase #6	$74.52	8.807%	$81.083	$81.08	$81.10	$81.10
Purchase #7	$122.90	11.322%	$136.8147	$136.81	$136.80	$136.80
7 purchase totals =	$993.27		$1,063.4569	$1,063.45	$1,063.50	$1,063.50