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	$51.42	6.496%	$54.7602	$54.76	$54.75	$54.80
Purchase #2	$81.83	5.412%	$86.2586	$86.26	$86.25	$86.30
Purchase #3	$156.38	7.386%	$167.9302	$167.93	$167.95	$167.90
Purchase #4	$248.89	12.843%	$280.8549	$280.85	$280.85	$280.90
Purchase #5	$154.51	4.556%	$161.5495	$161.55	$161.55	$161.50
Purchase #6	$205.50	8.724%	$223.4278	$223.43	$223.45	$223.40
Purchase #7	$70.94	9.550%	$77.7148	$77.71	$77.70	$77.70
7 purchase totals =	$969.47		$1,052.4960	$1,052.49	$1,052.50	$1,052.50