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	$212.54	9.750%	$233.2627	$233.26	$233.25	$233.30
Purchase #2	$62.53	3.345%	$64.6216	$64.62	$64.60	$64.60
Purchase #3	$144.90	13.782%	$164.8701	$164.87	$164.85	$164.90
Purchase #4	$139.85	6.109%	$148.3934	$148.39	$148.40	$148.40
Purchase #5	$242.61	3.617%	$251.3852	$251.39	$251.40	$251.40
Purchase #6	$42.29	3.586%	$43.8065	$43.81	$43.80	$43.80
Purchase #7	$237.90	9.649%	$260.855	$260.86	$260.85	$260.90
7 purchase totals =	$1,082.62		$1,167.1945	$1,167.20	$1,167.15	$1,167.30