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	$223.57	4.569%	$233.7849	$233.78	$233.80	$233.80
Purchase #2	$58.95	12.598%	$66.3765	$66.38	$66.40	$66.40
Purchase #3	$116.93	12.667%	$131.7415	$131.74	$131.75	$131.70
Purchase #4	$134.94	5.849%	$142.8326	$142.83	$142.85	$142.80
Purchase #5	$103.87	7.171%	$111.3185	$111.32	$111.30	$111.30
Purchase #6	$160.44	12.127%	$179.8966	$179.90	$179.90	$179.90
Purchase #7	$179.25	9.581%	$196.4239	$196.42	$196.40	$196.40
7 purchase totals =	$977.95		$1,062.3745	$1,062.37	$1,062.40	$1,062.30