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	$218.31	13.278%	$247.2972	$247.30	$247.30	$247.30
Purchase #2	$222.53	11.823%	$248.8397	$248.84	$248.85	$248.80
Purchase #3	$190.82	9.233%	$208.4384	$208.44	$208.45	$208.40
Purchase #4	$87.29	8.347%	$94.5761	$94.58	$94.60	$94.60
Purchase #5	$36.67	12.346%	$41.1973	$41.20	$41.20	$41.20
Purchase #6	$222.72	6.366%	$236.8984	$236.90	$236.90	$236.90
Purchase #7	$109.89	8.774%	$119.5317	$119.53	$119.55	$119.50
7 purchase totals =	$1,088.23		$1,196.7788	$1,196.79	$1,196.85	$1,196.70