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	$70.59	10.617%	$78.0845	$78.08	$78.10	$78.10
Purchase #2	$61.90	5.129%	$65.0749	$65.07	$65.05	$65.10
Purchase #3	$208.56	4.162%	$217.2403	$217.24	$217.25	$217.20
Purchase #4	$186.50	13.414%	$211.5171	$211.52	$211.50	$211.50
Purchase #5	$107.86	3.836%	$111.9975	$112.00	$112.00	$112.00
Purchase #6	$78.76	12.337%	$88.4766	$88.48	$88.50	$88.50
Purchase #7	$231.70	13.558%	$263.1139	$263.11	$263.10	$263.10
7 purchase totals =	$945.87		$1,035.5048	$1,035.50	$1,035.50	$1,035.50