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	$43.26	9.287%	$47.2776	$47.28	$47.30	$47.30
Purchase #2	$112.39	13.806%	$127.9066	$127.91	$127.90	$127.90
Purchase #3	$245.77	5.543%	$259.393	$259.39	$259.40	$259.40
Purchase #4	$187.71	9.346%	$205.2534	$205.25	$205.25	$205.30
Purchase #5	$219.79	6.836%	$234.8148	$234.81	$234.80	$234.80
Purchase #6	$150.66	10.589%	$166.6134	$166.61	$166.60	$166.60
Purchase #7	$9.79	8.196%	$10.5924	$10.59	$10.60	$10.60
7 purchase totals =	$969.37		$1,051.8512	$1,051.84	$1,051.85	$1,051.90