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	$32.80	7.858%	$35.3774	$35.38	$35.40	$35.40
Purchase #2	$232.85	12.710%	$262.4452	$262.45	$262.45	$262.40
Purchase #3	$102.84	6.619%	$109.647	$109.65	$109.65	$109.60
Purchase #4	$151.81	13.682%	$172.5806	$172.58	$172.60	$172.60
Purchase #5	$73.49	8.484%	$79.7249	$79.72	$79.70	$79.70
Purchase #6	$165.53	13.179%	$187.3452	$187.35	$187.35	$187.30
Purchase #7	$239.44	10.577%	$264.7656	$264.77	$264.75	$264.80
7 purchase totals =	$998.76		$1,111.8859	$1,111.90	$1,111.90	$1,111.80