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	$50.52	4.169%	$52.6262	$52.63	$52.65	$52.60
Purchase #2	$141.52	10.447%	$156.3046	$156.30	$156.30	$156.30
Purchase #3	$194.83	7.165%	$208.7896	$208.79	$208.80	$208.80
Purchase #4	$69.79	12.849%	$78.7573	$78.76	$78.75	$78.80
Purchase #5	$56.80	13.263%	$64.3334	$64.33	$64.35	$64.30
Purchase #6	$246.25	13.456%	$279.3854	$279.39	$279.40	$279.40
Purchase #7	$41.31	11.532%	$46.0739	$46.07	$46.05	$46.10
7 purchase totals =	$801.02		$886.2704	$886.27	$886.30	$886.30