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	$119.47	7.398%	$128.3084	$128.31	$128.30	$128.30
Purchase #2	$93.34	8.509%	$101.2823	$101.28	$101.30	$101.30
Purchase #3	$59.72	10.176%	$65.7971	$65.80	$65.80	$65.80
Purchase #4	$248.51	9.798%	$272.859	$272.86	$272.85	$272.90
Purchase #5	$107.38	8.347%	$116.343	$116.34	$116.35	$116.30
Purchase #6	$248.30	8.854%	$270.2845	$270.28	$270.30	$270.30
Purchase #7	$131.58	7.493%	$141.4393	$141.44	$141.45	$141.40
7 purchase totals =	$1,008.30		$1,096.3136	$1,096.31	$1,096.35	$1,096.30