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	$23.34	8.232%	$25.2613	$25.26	$25.25	$25.30
Purchase #2	$81.36	13.766%	$92.56	$92.56	$92.55	$92.60
Purchase #3	$243.35	12.164%	$272.9511	$272.95	$272.95	$273.00
Purchase #4	$227.99	10.254%	$251.3681	$251.37	$251.35	$251.40
Purchase #5	$85.86	4.152%	$89.4249	$89.42	$89.40	$89.40
Purchase #6	$166.86	13.601%	$189.5546	$189.55	$189.55	$189.60
Purchase #7	$143.95	8.692%	$156.4621	$156.46	$156.45	$156.50
7 purchase totals =	$972.71		$1,077.5821	$1,077.57	$1,077.50	$1,077.80