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	$215.85	10.216%	$237.9012	$237.90	$237.90	$237.90
Purchase #2	$159.83	9.536%	$175.0714	$175.07	$175.05	$175.10
Purchase #3	$248.51	5.793%	$262.9062	$262.91	$262.90	$262.90
Purchase #4	$38.59	11.851%	$43.1633	$43.16	$43.15	$43.20
Purchase #5	$229.87	9.448%	$251.5881	$251.59	$251.60	$251.60
Purchase #6	$87.32	13.529%	$99.1335	$99.13	$99.15	$99.10
Purchase #7	$83.38	13.349%	$94.5104	$94.51	$94.50	$94.50
7 purchase totals =	$1,063.35		$1,164.2741	$1,164.27	$1,164.25	$1,164.30