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	$238.46	10.225%	$262.8425	$262.84	$262.85	$262.80
Purchase #2	$127.30	9.516%	$139.4139	$139.41	$139.40	$139.40
Purchase #3	$204.61	3.558%	$211.89	$211.89	$211.90	$211.90
Purchase #4	$201.40	5.152%	$211.7761	$211.78	$211.80	$211.80
Purchase #5	$94.49	9.523%	$103.4883	$103.49	$103.50	$103.50
Purchase #6	$37.90	13.366%	$42.9657	$42.97	$42.95	$43.00
Purchase #7	$112.76	7.106%	$120.7727	$120.77	$120.75	$120.80
7 purchase totals =	$1,016.92		$1,093.1492	$1,093.15	$1,093.15	$1,093.20