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	$153.81	12.824%	$173.5346	$173.53	$173.55	$173.50
Purchase #2	$176.84	3.268%	$182.6191	$182.62	$182.60	$182.60
Purchase #3	$202.26	11.164%	$224.8403	$224.84	$224.85	$224.80
Purchase #4	$136.51	4.620%	$142.8168	$142.82	$142.80	$142.80
Purchase #5	$62.97	13.642%	$71.5604	$71.56	$71.55	$71.60
Purchase #6	$143.80	13.156%	$162.7183	$162.72	$162.70	$162.70
Purchase #7	$36.89	7.175%	$39.5369	$39.54	$39.55	$39.50
7 purchase totals =	$913.08		$997.6264	$997.63	$997.60	$997.50