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	$137.28	5.848%	$145.3081	$145.31	$145.30	$145.30
Purchase #2	$216.91	8.612%	$235.5903	$235.59	$235.60	$235.60
Purchase #3	$190.60	4.648%	$199.4591	$199.46	$199.45	$199.50
Purchase #4	$234.80	8.725%	$255.2863	$255.29	$255.30	$255.30
Purchase #5	$107.67	10.840%	$119.3414	$119.34	$119.35	$119.30
Purchase #6	$131.76	4.333%	$137.4692	$137.47	$137.45	$137.50
Purchase #7	$245.97	9.178%	$268.5451	$268.55	$268.55	$268.50
7 purchase totals =	$1,264.99		$1,360.9995	$1,361.01	$1,361.00	$1,361.00