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	$249.95	4.496%	$261.1878	$261.19	$261.20	$261.20
Purchase #2	$159.27	9.358%	$174.1745	$174.17	$174.15	$174.20
Purchase #3	$107.90	4.258%	$112.4944	$112.49	$112.50	$112.50
Purchase #4	$98.83	13.440%	$112.1128	$112.11	$112.10	$112.10
Purchase #5	$40.88	13.184%	$46.2696	$46.27	$46.25	$46.30
Purchase #6	$95.43	5.570%	$100.7455	$100.75	$100.75	$100.70
Purchase #7	$202.67	6.439%	$215.7199	$215.72	$215.70	$215.70
7 purchase totals =	$954.93		$1,022.7045	$1,022.70	$1,022.65	$1,022.70