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	$161.64	10.498%	$178.609	$178.61	$178.60	$178.60
Purchase #2	$215.72	4.286%	$224.9658	$224.97	$224.95	$225.00
Purchase #3	$56.38	9.212%	$61.5737	$61.57	$61.55	$61.60
Purchase #4	$61.89	9.238%	$67.6074	$67.61	$67.60	$67.60
Purchase #5	$98.88	9.161%	$107.9384	$107.94	$107.95	$107.90
Purchase #6	$59.66	9.627%	$65.4035	$65.40	$65.40	$65.40
Purchase #7	$74.51	8.581%	$80.9037	$80.90	$80.90	$80.90
7 purchase totals =	$728.68		$787.0015	$787.00	$786.95	$787.00