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	$12.36	12.693%	$13.9289	$13.93	$13.95	$13.90
Purchase #2	$48.68	13.725%	$55.3613	$55.36	$55.35	$55.40
Purchase #3	$111.39	13.467%	$126.3909	$126.39	$126.40	$126.40
Purchase #4	$211.51	10.387%	$233.4795	$233.48	$233.50	$233.50
Purchase #5	$222.71	4.756%	$233.3021	$233.30	$233.30	$233.30
Purchase #6	$102.69	6.688%	$109.5579	$109.56	$109.55	$109.60
Purchase #7	$47.70	7.477%	$51.2665	$51.27	$51.25	$51.30
7 purchase totals =	$757.04		$823.2871	$823.29	$823.30	$823.40