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	$93.98	10.630%	$103.9701	$103.97	$103.95	$104.00
Purchase #2	$116.63	9.418%	$127.6142	$127.61	$127.60	$127.60
Purchase #3	$25.68	10.139%	$28.2837	$28.28	$28.30	$28.30
Purchase #4	$183.43	3.532%	$189.9087	$189.91	$189.90	$189.90
Purchase #5	$123.97	11.822%	$138.6257	$138.63	$138.65	$138.60
Purchase #6	$112.50	4.601%	$117.6761	$117.68	$117.70	$117.70
Purchase #7	$60.40	12.270%	$67.8111	$67.81	$67.80	$67.80
7 purchase totals =	$716.59		$773.8896	$773.89	$773.90	$773.90