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	$208.32	13.508%	$236.4599	$236.46	$236.45	$236.50
Purchase #2	$19.32	11.502%	$21.5422	$21.54	$21.55	$21.50
Purchase #3	$25.61	7.786%	$27.604	$27.60	$27.60	$27.60
Purchase #4	$49.37	6.590%	$52.6235	$52.62	$52.60	$52.60
Purchase #5	$127.29	10.614%	$140.8006	$140.80	$140.80	$140.80
Purchase #6	$248.74	9.781%	$273.0693	$273.07	$273.05	$273.10
Purchase #7	$109.45	8.191%	$118.415	$118.42	$118.40	$118.40
7 purchase totals =	$788.10		$870.5145	$870.51	$870.45	$870.50