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	$118.47	4.105%	$123.3332	$123.33	$123.35	$123.30
Purchase #2	$109.52	10.692%	$121.2299	$121.23	$121.25	$121.20
Purchase #3	$70.94	7.273%	$76.0995	$76.10	$76.10	$76.10
Purchase #4	$78.96	13.795%	$89.8525	$89.85	$89.85	$89.90
Purchase #5	$177.43	5.333%	$186.8923	$186.89	$186.90	$186.90
Purchase #6	$183.61	5.230%	$193.2128	$193.21	$193.20	$193.20
Purchase #7	$87.83	8.386%	$95.1954	$95.20	$95.20	$95.20
7 purchase totals =	$826.76		$885.8156	$885.81	$885.85	$885.80