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	$52.64	3.444%	$54.4529	$54.45	$54.45	$54.50
Purchase #2	$105.26	6.464%	$112.064	$112.06	$112.05	$112.10
Purchase #3	$70.80	11.438%	$78.8981	$78.90	$78.90	$78.90
Purchase #4	$229.91	11.842%	$257.1359	$257.14	$257.15	$257.10
Purchase #5	$129.59	10.473%	$143.162	$143.16	$143.15	$143.20
Purchase #6	$90.83	4.686%	$95.0863	$95.09	$95.10	$95.10
Purchase #7	$169.79	6.649%	$181.0793	$181.08	$181.10	$181.10
7 purchase totals =	$848.82		$921.8785	$921.88	$921.90	$922.00