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	$238.45	11.761%	$266.4941	$266.49	$266.50	$266.50
Purchase #2	$16.80	10.818%	$18.6174	$18.62	$18.60	$18.60
Purchase #3	$54.39	5.780%	$57.5337	$57.53	$57.55	$57.50
Purchase #4	$184.51	11.383%	$205.5128	$205.51	$205.50	$205.50
Purchase #5	$217.99	12.179%	$244.539	$244.54	$244.55	$244.50
Purchase #6	$242.89	6.398%	$258.4301	$258.43	$258.45	$258.40
Purchase #7	$6.75	9.865%	$7.4159	$7.42	$7.40	$7.40
7 purchase totals =	$961.78		$1,058.5430	$1,058.54	$1,058.55	$1,058.40