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	$32.39	3.541%	$33.5369	$33.54	$33.55	$33.50
Purchase #2	$195.78	11.299%	$217.9012	$217.90	$217.90	$217.90
Purchase #3	$70.94	5.169%	$74.6069	$74.61	$74.60	$74.60
Purchase #4	$11.79	5.264%	$12.4106	$12.41	$12.40	$12.40
Purchase #5	$18.41	10.370%	$20.3191	$20.32	$20.30	$20.30
Purchase #6	$47.82	7.446%	$51.3807	$51.38	$51.40	$51.40
Purchase #7	$45.93	10.705%	$50.8468	$50.85	$50.85	$50.80
7 purchase totals =	$423.06		$461.0022	$461.01	$461.00	$460.90