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	$112.88	13.860%	$128.5252	$128.53	$128.55	$128.50
Purchase #2	$155.51	8.114%	$168.1281	$168.13	$168.15	$168.10
Purchase #3	$189.50	7.737%	$204.1616	$204.16	$204.15	$204.20
Purchase #4	$236.55	6.503%	$251.9328	$251.93	$251.95	$251.90
Purchase #5	$21.70	11.600%	$24.2172	$24.22	$24.20	$24.20
Purchase #6	$30.38	5.141%	$31.9418	$31.94	$31.95	$31.90
Purchase #7	$231.97	10.130%	$255.4686	$255.47	$255.45	$255.50
7 purchase totals =	$978.49		$1,064.3753	$1,064.38	$1,064.40	$1,064.30