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	$60.57	6.649%	$64.5973	$64.60	$64.60	$64.60
Purchase #2	$171.76	10.105%	$189.1163	$189.12	$189.10	$189.10
Purchase #3	$179.62	13.588%	$204.0268	$204.03	$204.05	$204.00
Purchase #4	$123.40	10.384%	$136.2139	$136.21	$136.20	$136.20
Purchase #5	$38.41	12.179%	$43.088	$43.09	$43.10	$43.10
Purchase #6	$206.80	7.553%	$222.4196	$222.42	$222.40	$222.40
Purchase #7	$177.33	10.657%	$196.2281	$196.23	$196.25	$196.20
7 purchase totals =	$957.89		$1,055.6900	$1,055.70	$1,055.70	$1,055.60