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	$69.70	9.148%	$76.0762	$76.08	$76.10	$76.10
Purchase #2	$74.29	5.664%	$78.4978	$78.50	$78.50	$78.50
Purchase #3	$159.60	11.370%	$177.7465	$177.75	$177.75	$177.70
Purchase #4	$59.52	13.782%	$67.723	$67.72	$67.70	$67.70
Purchase #5	$90.85	5.135%	$95.5151	$95.52	$95.50	$95.50
Purchase #6	$136.96	11.297%	$152.4324	$152.43	$152.45	$152.40
Purchase #7	$206.81	11.701%	$231.0088	$231.01	$231.00	$231.00
7 purchase totals =	$797.73		$878.9998	$879.01	$879.00	$878.90