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	$200.89	3.834%	$208.5921	$208.59	$208.60	$208.60
Purchase #2	$123.77	13.826%	$140.8824	$140.88	$140.90	$140.90
Purchase #3	$176.45	5.488%	$186.1336	$186.13	$186.15	$186.10
Purchase #4	$245.41	5.262%	$258.3235	$258.32	$258.30	$258.30
Purchase #5	$35.79	6.747%	$38.2048	$38.20	$38.20	$38.20
Purchase #6	$60.43	5.249%	$63.602	$63.60	$63.60	$63.60
Purchase #7	$176.92	7.261%	$189.7662	$189.77	$189.75	$189.80
7 purchase totals =	$1,019.66		$1,085.5046	$1,085.49	$1,085.50	$1,085.50