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	$138.88	12.844%	$156.7177	$156.72	$156.70	$156.70
Purchase #2	$188.30	4.267%	$196.3348	$196.33	$196.35	$196.30
Purchase #3	$61.68	12.195%	$69.2019	$69.20	$69.20	$69.20
Purchase #4	$121.59	5.457%	$128.2252	$128.23	$128.25	$128.20
Purchase #5	$136.33	10.643%	$150.8396	$150.84	$150.85	$150.80
Purchase #6	$88.33	10.450%	$97.5605	$97.56	$97.55	$97.60
Purchase #7	$227.42	12.739%	$256.391	$256.39	$256.40	$256.40
7 purchase totals =	$962.53		$1,055.2707	$1,055.27	$1,055.30	$1,055.20