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	$41.70	3.807%	$43.2875	$43.29	$43.30	$43.30
Purchase #2	$47.31	10.554%	$52.3031	$52.30	$52.30	$52.30
Purchase #3	$228.84	12.252%	$256.8775	$256.88	$256.90	$256.90
Purchase #4	$164.93	3.408%	$170.5508	$170.55	$170.55	$170.60
Purchase #5	$54.25	4.355%	$56.6126	$56.61	$56.60	$56.60
Purchase #6	$117.43	9.620%	$128.7268	$128.73	$128.75	$128.70
Purchase #7	$198.52	7.566%	$213.54	$213.54	$213.55	$213.50
7 purchase totals =	$852.98		$921.8983	$921.90	$921.95	$921.90