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	$59.88	13.417%	$67.9141	$67.91	$67.90	$67.90
Purchase #2	$235.75	5.758%	$249.3245	$249.32	$249.30	$249.30
Purchase #3	$75.47	9.437%	$82.5921	$82.59	$82.60	$82.60
Purchase #4	$224.49	11.167%	$249.5588	$249.56	$249.55	$249.60
Purchase #5	$245.72	8.565%	$266.7659	$266.77	$266.75	$266.80
Purchase #6	$198.90	4.610%	$208.0693	$208.07	$208.05	$208.10
Purchase #7	$82.83	8.315%	$89.7173	$89.72	$89.70	$89.70
7 purchase totals =	$1,123.04		$1,213.9420	$1,213.94	$1,213.85	$1,214.00