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	$118.81	4.689%	$124.381	$124.38	$124.40	$124.40
Purchase #2	$217.91	3.629%	$225.818	$225.82	$225.80	$225.80
Purchase #3	$52.72	8.704%	$57.3087	$57.31	$57.30	$57.30
Purchase #4	$168.67	7.587%	$181.467	$181.47	$181.45	$181.50
Purchase #5	$228.41	3.580%	$236.5871	$236.59	$236.60	$236.60
Purchase #6	$13.73	8.625%	$14.9142	$14.91	$14.90	$14.90
Purchase #7	$123.38	12.180%	$138.4077	$138.41	$138.40	$138.40
7 purchase totals =	$923.63		$978.8837	$978.89	$978.85	$978.90