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	$22.70	12.757%	$25.5958	$25.60	$25.60	$25.60
Purchase #2	$111.59	4.607%	$116.731	$116.73	$116.75	$116.70
Purchase #3	$57.38	9.472%	$62.815	$62.82	$62.80	$62.80
Purchase #4	$126.38	12.364%	$142.0056	$142.01	$142.00	$142.00
Purchase #5	$162.39	11.713%	$181.4107	$181.41	$181.40	$181.40
Purchase #6	$245.30	4.585%	$256.547	$256.55	$256.55	$256.50
Purchase #7	$224.29	8.300%	$242.9061	$242.91	$242.90	$242.90
7 purchase totals =	$950.03		$1,028.0112	$1,028.03	$1,028.00	$1,027.90