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	$136.31	5.109%	$143.2741	$143.27	$143.25	$143.30
Purchase #2	$105.68	6.798%	$112.8641	$112.86	$112.85	$112.90
Purchase #3	$176.59	6.219%	$187.5721	$187.57	$187.55	$187.60
Purchase #4	$153.62	13.208%	$173.9101	$173.91	$173.90	$173.90
Purchase #5	$189.85	3.591%	$196.6675	$196.67	$196.65	$196.70
Purchase #6	$109.39	5.762%	$115.6931	$115.69	$115.70	$115.70
Purchase #7	$114.68	7.215%	$122.9542	$122.95	$122.95	$123.00
7 purchase totals =	$986.12		$1,052.9352	$1,052.92	$1,052.85	$1,053.10