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	$148.34	7.131%	$158.9181	$158.92	$158.90	$158.90
Purchase #2	$36.44	13.402%	$41.3237	$41.32	$41.30	$41.30
Purchase #3	$97.58	12.542%	$109.8185	$109.82	$109.80	$109.80
Purchase #4	$158.68	9.535%	$173.8101	$173.81	$173.80	$173.80
Purchase #5	$131.60	10.126%	$144.9258	$144.93	$144.95	$144.90
Purchase #6	$236.67	8.533%	$256.8651	$256.87	$256.85	$256.90
Purchase #7	$157.56	9.828%	$173.045	$173.05	$173.05	$173.00
7 purchase totals =	$966.87		$1,058.7063	$1,058.72	$1,058.65	$1,058.60