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	$54.74	9.513%	$59.9474	$59.95	$59.95	$59.90
Purchase #2	$66.72	10.643%	$73.821	$73.82	$73.80	$73.80
Purchase #3	$248.70	10.577%	$275.005	$275.01	$275.00	$275.00
Purchase #4	$24.28	11.720%	$27.1256	$27.13	$27.15	$27.10
Purchase #5	$164.69	3.189%	$169.942	$169.94	$169.95	$169.90
Purchase #6	$246.96	7.263%	$264.8967	$264.90	$264.90	$264.90
Purchase #7	$120.36	6.771%	$128.5096	$128.51	$128.50	$128.50
7 purchase totals =	$926.45		$999.2473	$999.26	$999.25	$999.10