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	$96.76	9.419%	$105.8738	$105.87	$105.85	$105.90
Purchase #2	$105.73	3.187%	$109.0996	$109.10	$109.10	$109.10
Purchase #3	$194.45	7.714%	$209.4499	$209.45	$209.45	$209.40
Purchase #4	$225.40	5.723%	$238.2996	$238.30	$238.30	$238.30
Purchase #5	$146.78	3.387%	$151.7514	$151.75	$151.75	$151.80
Purchase #6	$20.38	5.585%	$21.5182	$21.52	$21.50	$21.50
Purchase #7	$235.90	8.328%	$255.5458	$255.55	$255.55	$255.50
7 purchase totals =	$1,025.40		$1,091.5383	$1,091.54	$1,091.50	$1,091.50