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	$139.62	3.462%	$144.4536	$144.45	$144.45	$144.50
Purchase #2	$125.31	4.331%	$130.7372	$130.74	$130.75	$130.70
Purchase #3	$229.82	12.676%	$258.952	$258.95	$258.95	$259.00
Purchase #4	$127.43	13.408%	$144.5158	$144.52	$144.50	$144.50
Purchase #5	$20.49	4.838%	$21.4813	$21.48	$21.50	$21.50
Purchase #6	$130.81	4.656%	$136.9005	$136.90	$136.90	$136.90
Purchase #7	$54.39	5.693%	$57.4864	$57.49	$57.50	$57.50
7 purchase totals =	$827.87		$894.5268	$894.53	$894.55	$894.60