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	$84.32	6.269%	$89.606	$89.61	$89.60	$89.60
Purchase #2	$162.62	3.212%	$167.8434	$167.84	$167.85	$167.80
Purchase #3	$177.77	12.867%	$200.6437	$200.64	$200.65	$200.60
Purchase #4	$47.85	5.459%	$50.4621	$50.46	$50.45	$50.50
Purchase #5	$210.68	7.730%	$226.9656	$226.97	$226.95	$227.00
Purchase #6	$38.30	7.276%	$41.0867	$41.09	$41.10	$41.10
Purchase #7	$234.61	9.248%	$256.3067	$256.31	$256.30	$256.30
7 purchase totals =	$956.15		$1,032.9142	$1,032.92	$1,032.90	$1,032.90