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	$217.49	12.611%	$244.9177	$244.92	$244.90	$244.90
Purchase #2	$193.75	8.296%	$209.8235	$209.82	$209.80	$209.80
Purchase #3	$65.34	3.429%	$67.5805	$67.58	$67.60	$67.60
Purchase #4	$162.41	9.861%	$178.4253	$178.43	$178.45	$178.40
Purchase #5	$48.95	13.549%	$55.5822	$55.58	$55.60	$55.60
Purchase #6	$121.45	8.347%	$131.5874	$131.59	$131.60	$131.60
Purchase #7	$152.93	3.640%	$158.4967	$158.50	$158.50	$158.50
7 purchase totals =	$962.32		$1,046.4133	$1,046.42	$1,046.45	$1,046.40