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	$35.69	5.379%	$37.6098	$37.61	$37.60	$37.60
Purchase #2	$38.29	12.810%	$43.1949	$43.19	$43.20	$43.20
Purchase #3	$29.83	10.268%	$32.8929	$32.89	$32.90	$32.90
Purchase #4	$180.79	12.445%	$203.2893	$203.29	$203.30	$203.30
Purchase #5	$160.70	9.221%	$175.5181	$175.52	$175.50	$175.50
Purchase #6	$46.86	7.164%	$50.2171	$50.22	$50.20	$50.20
Purchase #7	$235.50	11.380%	$262.2999	$262.30	$262.30	$262.30
7 purchase totals =	$727.66		$805.0220	$805.02	$805.00	$805.00