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	$184.39	6.775%	$196.8824	$196.88	$196.90	$196.90
Purchase #2	$109.43	7.184%	$117.2915	$117.29	$117.30	$117.30
Purchase #3	$61.99	13.834%	$70.5657	$70.57	$70.55	$70.60
Purchase #4	$15.62	11.412%	$17.4026	$17.40	$17.40	$17.40
Purchase #5	$46.38	10.667%	$51.3274	$51.33	$51.35	$51.30
Purchase #6	$215.86	10.634%	$238.8146	$238.81	$238.80	$238.80
Purchase #7	$111.92	6.607%	$119.3146	$119.31	$119.30	$119.30
7 purchase totals =	$745.59		$811.5988	$811.59	$811.60	$811.60