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	$247.72	4.223%	$258.1812	$258.18	$258.20	$258.20
Purchase #2	$29.27	10.719%	$32.4075	$32.41	$32.40	$32.40
Purchase #3	$187.43	4.750%	$196.3329	$196.33	$196.35	$196.30
Purchase #4	$159.67	13.629%	$181.4314	$181.43	$181.45	$181.40
Purchase #5	$45.79	12.188%	$51.3709	$51.37	$51.35	$51.40
Purchase #6	$234.66	3.609%	$243.1289	$243.13	$243.15	$243.10
Purchase #7	$139.41	12.460%	$156.7805	$156.78	$156.80	$156.80
7 purchase totals =	$1,043.95		$1,119.6333	$1,119.63	$1,119.70	$1,119.60