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	$19.93	12.480%	$22.4173	$22.42	$22.40	$22.40
Purchase #2	$182.54	12.526%	$205.405	$205.41	$205.40	$205.40
Purchase #3	$167.45	12.816%	$188.9104	$188.91	$188.90	$188.90
Purchase #4	$131.79	5.611%	$139.1847	$139.18	$139.20	$139.20
Purchase #5	$47.94	11.619%	$53.5101	$53.51	$53.50	$53.50
Purchase #6	$245.54	6.795%	$262.2244	$262.22	$262.20	$262.20
Purchase #7	$173.66	9.384%	$189.9563	$189.96	$189.95	$190.00
7 purchase totals =	$968.85		$1,061.6082	$1,061.61	$1,061.55	$1,061.60