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	$38.31	13.209%	$43.3704	$43.37	$43.35	$43.40
Purchase #2	$119.37	11.868%	$133.5368	$133.54	$133.55	$133.50
Purchase #3	$181.95	6.729%	$194.1934	$194.19	$194.20	$194.20
Purchase #4	$153.66	5.678%	$162.3848	$162.38	$162.40	$162.40
Purchase #5	$202.78	10.713%	$224.5038	$224.50	$224.50	$224.50
Purchase #6	$86.49	11.699%	$96.6085	$96.61	$96.60	$96.60
Purchase #7	$74.59	5.533%	$78.7171	$78.72	$78.70	$78.70
7 purchase totals =	$857.15		$933.3148	$933.31	$933.30	$933.30