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	$237.92	6.444%	$253.2516	$253.25	$253.25	$253.30
Purchase #2	$61.45	4.191%	$64.0254	$64.03	$64.05	$64.00
Purchase #3	$111.70	7.216%	$119.7603	$119.76	$119.75	$119.80
Purchase #4	$54.94	7.390%	$59.0001	$59.00	$59.00	$59.00
Purchase #5	$123.92	6.208%	$131.613	$131.61	$131.60	$131.60
Purchase #6	$124.95	10.405%	$137.951	$137.95	$137.95	$138.00
Purchase #7	$193.85	6.524%	$206.4968	$206.50	$206.50	$206.50
7 purchase totals =	$908.73		$972.0982	$972.10	$972.10	$972.20