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	$38.89	12.547%	$43.7695	$43.77	$43.75	$43.80
Purchase #2	$102.42	13.709%	$116.4608	$116.46	$116.45	$116.50
Purchase #3	$187.33	13.274%	$212.1962	$212.20	$212.20	$212.20
Purchase #4	$98.99	13.463%	$112.317	$112.32	$112.30	$112.30
Purchase #5	$211.54	9.864%	$232.4063	$232.41	$232.40	$232.40
Purchase #6	$150.41	10.109%	$165.6149	$165.61	$165.60	$165.60
Purchase #7	$201.93	10.244%	$222.6157	$222.62	$222.60	$222.60
7 purchase totals =	$991.51		$1,105.3804	$1,105.39	$1,105.30	$1,105.40