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	$41.78	3.229%	$43.1291	$43.13	$43.15	$43.10
Purchase #2	$227.42	13.484%	$258.0853	$258.09	$258.10	$258.10
Purchase #3	$205.73	13.778%	$234.0755	$234.08	$234.10	$234.10
Purchase #4	$32.39	7.367%	$34.7762	$34.78	$34.80	$34.80
Purchase #5	$88.69	13.455%	$100.6232	$100.62	$100.60	$100.60
Purchase #6	$5.69	8.333%	$6.1641	$6.16	$6.15	$6.20
Purchase #7	$80.57	10.779%	$89.2546	$89.25	$89.25	$89.30
7 purchase totals =	$682.27		$766.1080	$766.11	$766.15	$766.20