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	$61.49	6.489%	$65.4801	$65.48	$65.50	$65.50
Purchase #2	$189.45	11.264%	$210.7896	$210.79	$210.80	$210.80
Purchase #3	$171.41	13.719%	$194.9257	$194.93	$194.95	$194.90
Purchase #4	$57.37	8.524%	$62.2602	$62.26	$62.25	$62.30
Purchase #5	$143.42	5.514%	$151.3282	$151.33	$151.35	$151.30
Purchase #6	$160.95	4.159%	$167.6439	$167.64	$167.65	$167.60
Purchase #7	$184.41	3.364%	$190.6136	$190.61	$190.60	$190.60
7 purchase totals =	$968.50		$1,043.0413	$1,043.04	$1,043.10	$1,043.00