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	$55.90	12.439%	$62.8534	$62.85	$62.85	$62.90
Purchase #2	$118.81	10.860%	$131.7128	$131.71	$131.70	$131.70
Purchase #3	$107.49	6.556%	$114.537	$114.54	$114.55	$114.50
Purchase #4	$179.49	9.247%	$196.0874	$196.09	$196.10	$196.10
Purchase #5	$181.66	9.140%	$198.2637	$198.26	$198.25	$198.30
Purchase #6	$230.30	7.478%	$247.5218	$247.52	$247.50	$247.50
Purchase #7	$47.96	4.467%	$50.1024	$50.10	$50.10	$50.10
7 purchase totals =	$921.61		$1,001.0785	$1,001.07	$1,001.05	$1,001.10