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	$218.59	12.480%	$245.87	$245.87	$245.85	$245.90
Purchase #2	$196.54	4.770%	$205.915	$205.92	$205.90	$205.90
Purchase #3	$42.86	10.105%	$47.191	$47.19	$47.20	$47.20
Purchase #4	$38.61	12.331%	$43.371	$43.37	$43.35	$43.40
Purchase #5	$38.81	9.423%	$42.4671	$42.47	$42.45	$42.50
Purchase #6	$228.55	7.344%	$245.3347	$245.33	$245.35	$245.30
Purchase #7	$242.33	11.784%	$270.8862	$270.89	$270.90	$270.90
7 purchase totals =	$1,006.29		$1,101.0350	$1,101.04	$1,101.00	$1,101.10