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	$218.96	11.810%	$244.8192	$244.82	$244.80	$244.80
Purchase #2	$179.76	5.438%	$189.5353	$189.54	$189.55	$189.50
Purchase #3	$210.65	9.329%	$230.3015	$230.30	$230.30	$230.30
Purchase #4	$19.57	3.813%	$20.3162	$20.32	$20.30	$20.30
Purchase #5	$66.57	6.787%	$71.0881	$71.09	$71.10	$71.10
Purchase #6	$92.49	8.638%	$100.4793	$100.48	$100.50	$100.50
Purchase #7	$155.42	13.729%	$176.7576	$176.76	$176.75	$176.80
7 purchase totals =	$943.42		$1,033.2972	$1,033.31	$1,033.30	$1,033.30