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	$150.64	9.646%	$165.1707	$165.17	$165.15	$165.20
Purchase #2	$86.67	9.155%	$94.6046	$94.60	$94.60	$94.60
Purchase #3	$128.39	3.170%	$132.46	$132.46	$132.45	$132.50
Purchase #4	$214.82	11.545%	$239.621	$239.62	$239.60	$239.60
Purchase #5	$105.94	4.827%	$111.0537	$111.05	$111.05	$111.10
Purchase #6	$231.47	7.556%	$248.9599	$248.96	$248.95	$249.00
Purchase #7	$87.84	6.417%	$93.4767	$93.48	$93.50	$93.50
7 purchase totals =	$1,005.77		$1,085.3466	$1,085.34	$1,085.30	$1,085.50